CINXE.COM

Just a moment...

<!DOCTYPE html><html lang="en-US"><head><title>Just a moment...</title><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=Edge"><meta name="robots" content="noindex,nofollow"><meta name="viewport" content="width=device-width,initial-scale=1"><style>*{box-sizing:border-box;margin:0;padding:0}html{line-height:1.15;-webkit-text-size-adjust:100%;color:#313131;font-family:system-ui,-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,Helvetica Neue,Arial,Noto Sans,sans-serif,Apple Color Emoji,Segoe UI Emoji,Segoe UI Symbol,Noto Color Emoji}body{display:flex;flex-direction:column;height:100vh;min-height:100vh}.main-content{margin:8rem auto;max-width:60rem;padding-left:1.5rem}@media (width <= 720px){.main-content{margin-top:4rem}}.h2{font-size:1.5rem;font-weight:500;line-height:2.25rem}@media (width <= 720px){.h2{font-size:1.25rem;line-height:1.5rem}}#challenge-error-text{background-image:url(data:image/svg+xml;base64,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);background-repeat:no-repeat;background-size:contain;padding-left:34px}@media (prefers-color-scheme:dark){body{background-color:#222;color:#d9d9d9}}</style><meta http-equiv="refresh" content="390"></head><body class="no-js"><div class="main-wrapper" role="main"><div class="main-content"><noscript><div class="h2"><span id="challenge-error-text">Enable JavaScript and cookies to continue</span></div></noscript></div></div><script>(function(){window._cf_chl_opt={cvId: '3',cZone: "dl.acm.org",cType: 'managed',cRay: '8e8e01bf0b54603f',cH: 'EISqOpZDo0OU_UJTxo0m8ece7fQWODLtWiIluTn3CA4-1732667396-1.2.1.1-eFqlPbqQ4pTr0I_5RAxe5dRMpapPtXAdZIx6r7qpvEebIQ0HR6NsyVUObe9Q12FB',cUPMDTk: "\/newsletter\/sigmod?__cf_chl_tk=ZY6rSn9FGHDc3jlB_wvMBdPj1kdonc2kSJ7tCH3XVSA-1732667396-1.0.1.1-eV43QzxrB3KlZzJKhcRsFKRBAQI5o2hf1oVeJ3BczJg",cFPWv: 'b',cITimeS: '1732667396',cTTimeMs: '1000',cMTimeMs: '390000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "",fa: "\/newsletter\/sigmod?__cf_chl_f_tk=ZY6rSn9FGHDc3jlB_wvMBdPj1kdonc2kSJ7tCH3XVSA-1732667396-1.0.1.1-eV43QzxrB3KlZzJKhcRsFKRBAQI5o2hf1oVeJ3BczJg",md: "mCgWMI3Hq1qKW7s7AhrnOZ.KrhvPXrNEUM7Pv64dLLg-1732667396-1.2.1.1-v2iHzEK7KgRRjaXD_G.7a6QC.Lk_TasmfqEBURq3Jwef8.6sC.0C1EcVQ2a4YXt.OwNEUJrSirOfdAt95xfTQdowJGGKS23R9VFNFbp.jzliralKCMwuhqW0zvNGZkxZVE6aRPXrwDnpHDZCFV5aiVhCK5w2WBPtSFph0B.TJj_EZ57dhYujoUoGs0Rbsi7j_FRZxqIa.AqzqkC3ucIrkOPfF5DaAePaQLSmMx3QNRN6.KfMR18O.MJ84T8QIfX.Xv3nqKm_TQHgTdCjuOSyooOfqvhhszuGEbXfo7rFYnYR6uaLkkjmyaYLNqU3EPoMkSD63LtYKIx7d2WGQBBagQCDCB8R7lcQPt5tlgoJvCyrW7bCo0lAxFmssDexHx173JxV4ldSfz.x8ekhMtTevnhkcTImOgCFh22DeRp4XH3lItLkgSLsrohenjR7lVr3wXmnKdJ0qNjeEeSyq5PaalPwWOU7.y8gMFpITwLjP1aWNHViQx4uGO6QKkTgVXEDylpiPuddsjNfZwSGQSS7jnzT2dOT50lmoQP1J4XSeD0jFCWuCyKg10djONt4c1EoxmtuiXFregAB7lqBIeNlrU2qOgB_sdUPdvQcyUaIXbRxV.nrh4nacXPW7noju.HEyvZe6hPlRJqfQ36JWGxJBdsyXdnU888Aj2MTh26pdEiiJ.b4QxASFf0iJt__uVOWjrME5ySVEJiJcppVJ0fe60r8sw1lrgoUNTUnt2HEU5N8USkllwkgZjd8kRIos8M1QWutHqGgcI1RTxRKt1db42SWx9U5j01wZIhipsLOhtPmxZyqIbUu6L9mAViSpsbfPoJEIoKPolrGqijaIcuG2h1VeQjcagkMplapIZzSa7A9eRh1SPbzSqQQw6bIdy8ucy.DfnqaFgC3V9UToK0gu1Kv5cgcyyTbJYq2kQUydjnIiR25jbRrb2r1DGxJbQxHcGp73at0_.iu.byo5zonw27OaRBXugSUijHBk9skMaXhtKowC_.pkO0rnylvfmfZuSirM3oWGQi00hCHVIWgLRCDEpfchcdZD1XgLAlqaaOXJTKHz7yxaOPotBF98FraS.B.d0D7.DIMTe3dn6eXk9gpAncUftI6zmwPB3jL6tjjQt_Mxtk5Mlnu0rSUUQSZgbLHTykDpnk1y8UMViUTNny3JR5RWdCy0rU28x.kOD2.EFlwOqJfhwwT2lKi6OD3qxQfEsOVm4AWIdU45.hpugQMXiIITe7ycB6TeDTj5j7cdTm5D39PNPKX_R2.KPsmg8iogtF0fBhAzO4enLb8d3XoCWygA_X2m5yRidPJaekOsk1FFExIb0xrf5.wlt8hhcyMfK71pqLqBNzjMdh8fxpT1MEfuZSHOUUdAigNVhYoyJvysxTk2dW.NKS2INYLQnnqeeK0Wzee5eLyi_RqvMgk4SHy6jmBeN2mVgA2CpnuxltrRI8FwiQ.WDYUh.J6gdjocxdCeIofqwW5t9NMg1hld5CWiQEN33pfwcoeqnpA8OJ_53pGBWWiCidIRHZqaR0V15zV7CcqYt0M67Bc0ihFnDprmsza00ZVlHWrMgL0zdw8URRXQMsZ4aDbd3fvpJB7Ssbi1KxSsEe.W9KlVTxzdcJub7PMSFfU0gQPeIiPYRjngpvlfZWovP5mlMuDjwwknvQbTcpLZzFlE5hmPpS5L6gkzdsUJu8JTmnSgXesn6uRy0aCu8kMnyxzCunGQCFFvwEw1m1oPblThAnVY8Knr7sicC4Xf1U1GXAdXJ4MwqyQcuPkSo1lm_oVc0iNfiHPiL7jaAwjIBXGam8Y2XQH1CsMBL4x2nass7Zx5krWjaw5xciVl470wutfJjzdm6cH2eMj1ugvIyByZeQOxFWHqLlXgMIQD8XLLyRDys6_Xu.jjFym6KSgcloo_yuzvGNgmZ2HMKoAE_88mLgzQpigBAiy9_6gXN4a_K0WxNddT2wBfisRvssxQqVfrb_VTSSOn.KI5kop8.DdK9Y.yNc3F03Y.b0h0NWoW4U4saxFvXN.WdIoqs7Zy0QJAXKPdkHKAsLaj3xFYaeLjX4bcI3Hl1lGz0ooDQ0ugFekNx7zyyG3fXkg5j5KYvA1Sskc1usuneZSCS5yFS3Vn9_RWWT9jhzrGMfEdEzFLVB3xXw3ft20YLhcCrGIyT20rABTjsoRazCWAlXOzU50MeBVK7e3bd.l1xMzkPKJfUhmBsBnfvpCKQ5X3VozZoVWuOK6EfCutzDtQSsz7WQFo47356lDgMUQ8wPb6YZkzqcRRB0ijMZxxr9cIQiAapWj0mP3iIJfFyubjXbwkZlqfaivXzcBCgi2E7zwEjg1skTfSVe.naM5hcNWxMYioqMRnUJoIPdSu0.WwGZvsExMYytHdrOr9mcOfzVjCDggyxZgHlmYJIfOQ_KPh1V2vqpShQP88mKFI8RKZf78hjIDMlVHy008321FJ5q.x6RdORGRseL3EHIv3mktHoFRU0gXfNW9V3QY7Ua2yoNQQFeDpriO2uGkWWiZ5NjhHL0JmjaKJI3mNarMAllTY7DDkFfeWv4fMCo0B0kR0xFuBGk3OM8ieDBxsdshL.cEAt3_GbKuEjLsKrtZAcR2uomirYiavfi9Mc15IODajsl4prYjABUEguwGlNz34i0zCreUFWVcLAUBOkf06NIM0wVioVWl67rrv5e8XLwgpT68unkKq29R.J21ShYr9QTwXzFDm4gKAp1h6MEia9cf3Kz7qGlzd.LJBwtlJKUt3grzGEPUCUiZEyB09PiLVepyigAz_F.y1ySUlO2YnSlQ9A.zXLaBqScDGEBWMeipad4HO2xAqwd6sFSBvgjQnlyeP0AUnD2C5wGsEzdX4ERZlYt6RiyidopJS7SibxJv2cxNGLi6BlUVhw_LDwsecVUL_ksPYKvca.cJS6pBmy0UdBHuf8fe.DhFWB0.QOadznp.wZQ_4OPKew",mdrd: "JsExz3HwOW9yvxbwjXQ83fUcTvQxeFu8BZ4bD8G8fD4-1732667396-1.2.1.1-WKlBw5kQCGGkThq5QMD33Hfj8YXMk3SuSojgvF0ZzOdm2srKFrdlMOKCPehViYNqn4tQL5ix.usEwWP8nGzzbvH2ByOAYgfyBhHRa9u67JSJ1EhoDi28ZgRjXTf4KPY.RrrFL.i_Dko996n1OHPoA.Tq1aKsRBtF4yOA.TuGfC1UTiYYgPvUFPDDWlCQIZjyQqCkNZLZjtM0gYJOQZhIpb.9ipFoPSZITA3.A6.HYOGCsSz8FAeubTq5dO5GkYQfkgOHfmyGziyz2mxbC55SN1_bKHX8V4U3skU0ihiEhfeLTafMyls7NynjL7ti.SOrEKYUYVyvu1Vza3cDviUWJo3LJpMAL14uj.WmXK_1IxOm5IAuNe1Dwjca.cdBwhwpykmofPRQ9DJSFbO7AbUbEtJd_IEX.2vSgZjU2fenWQPa29FtMCz7z4JmpSZog4k2O4mhL3uPyPHnqBkLTQuDaMAtgMg1rDjscKzlzkOo7191XHHiVr_PdlY5_neG5Z3VKvZDuPKnv7dFQxglwvNzRkuIDxHYRHerx8YhZO6ggl7gwr4pQtjLY3LkoygQVjhYyCbkLr4QdPPwhh19pP0rlT3Z9L.pd_nIsLkEyvR8svL9soWjRDSqB19i6aq.B_4qxNdXVsC0Sb6HPFQKgEjomWtZ4b8E3XEU6_znRNp2r6YttlWfSuAD3cYB_xsIapcerHqJfiltQUXSkNLg__0JJqO9wwfnN3RGubxwKr9O5YI2OdIRq96UIUvU6iAivnk8C4CBgE94BYr6rcIjzrffO4dTF_KLKCAndTJLm7k2N_fX8yyU1nziw90Yd3AtCZVJH7nDCH9WTGjn4LgWD2gfDmcG6EoPL0o42X1H_JtcnPkBakfp7o5goxbfbVQbG.Mzp4o4OCJ7WB86MCpa6g7JwpSG01Cykh87UIjun3.TsZ3zNCvq5cptbees1z9siUIJbALgxkjRjerTauPY31UhqfWfCagqENwsiE_9Nb65KSYylMyFRxDE9yaz_HYf_Y1FESXSqmJv8kDtzuR.q4sucrOzVRO0euu8waGqEJC3MO6kVpn8YsUmnOZNHFWJ.j8TXzJcylpdFLJJPvkN1V5cV8rgvtGyXb8MEbwGTyhEzKSnPdx7j6IonI48abZN0d7FMCttaTS2KN2LTmbhfkmuqkHaklfY6olIRKSvBlvZewWGtYGUr9ADSNDJfBAhEVXXjG9_OgyB0T4zkg_uXfBpoBXXbNwencOkPD_nZw9ybGpjislpK9uCOVnEmEn.xFX.VQ7bdx4AloRsRkyfn8uvXkXCbVSotl9okj3fzHFY803SYe9hNX5EXzSKBZHqEdAArBquoqcyZkqWYgHfbWEuQ93qWaCSbZ7oiOxMoZloRIvbi88ciysP.7OBkKwG97LF8YSRjzJ40AN0y4EI24KsEX8kqLkyn6WDKiRBsyYiy6PPrJ5Mfq36WaZKlKKj_Qb3gaYAJkqWr0GD5wEKHbzhr77QomSs40teispBrum34jyaFpDbJpMR53jy1hr50ZO5ALD06IWRI8ZQS8CHbHECnX0QwLxUdt_oEvwkr5Z59Tpm0JwssmBRhl7wtPKZRj4RzHWRGFm_QlQKrMAgeQqTJQxNGzDpJm2QVuQZsN60eXBDCerntdWHPsu62.6PeEokv.4uLc_qPSL7UdrbXQ62IkCrTzZzA3Thgk33QleK754KwQgCrsKUuS5kPL8n82W8vdxKIbLi0_r8nimI7TkWIVe6.m70TTW6ke53F7hIMYRT99bMuXhNQVKyDtcySZi30s61oGrKtgMeNnjcROvC9uHxIQpdaQyt2EGOW90pdJL1MEJdQJOAznE2NuC9v.Zl6wav7D0orN8lWhxaLE8Dx5IBXFpoVXC_x_WQQ0rqewgV1BzEwZD5aNDhAEifGKXWPlV4FozxqFcFwYahStN5Sc8xBKkdoMQ4ctDzhW.NULCZlGcugBBxLFLU5eDedNAu"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/b/orchestrate/chl_page/v1?ray=8e8e01bf0b54603f';window._cf_chl_opt.cOgUHash = location.hash === '' && location.href.indexOf('#') !== -1 ? '#' : location.hash;window._cf_chl_opt.cOgUQuery = location.search === '' && location.href.slice(0, location.href.length - window._cf_chl_opt.cOgUHash.length).indexOf('?') !== -1 ? '?' : location.search;if (window.history && window.history.replaceState) {var ogU = location.pathname + window._cf_chl_opt.cOgUQuery + window._cf_chl_opt.cOgUHash;history.replaceState(null, null, "\/newsletter\/sigmod?__cf_chl_rt_tk=ZY6rSn9FGHDc3jlB_wvMBdPj1kdonc2kSJ7tCH3XVSA-1732667396-1.0.1.1-eV43QzxrB3KlZzJKhcRsFKRBAQI5o2hf1oVeJ3BczJg" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>