CINXE.COM

<!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: "zbmath.org",cType: 'managed',cRay: '92d824fa7bb93e47',cH: 'Mz1_QRQGy8xLcS5jSGpK5h5JrI.uAqnhNTAv3GVzHaA-1744182204-1.2.1.1-vav0VX58d9.MlmhpoEn9kp6d..Ok2lGOM168sXGQDGMHvqhs7lwcAa8qEanmIy2O',cUPMDTk: "\/1544.93153?__cf_chl_tk=xk8nBAL2y8fkr_mCqWQgqfwf3YsHM0f7kEipurdgalM-1744182204-1.0.1.1-sDDn9Zwvv2Qz.LgUq9AJmu4p5lpjFFZkLNYrjiChVqE",cFPWv: 'g',cITimeS: '1744182204',cTTimeMs: '1000',cMTimeMs: '390000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "unsupported_browser_beacon",fa: "\/1544.93153?__cf_chl_f_tk=xk8nBAL2y8fkr_mCqWQgqfwf3YsHM0f7kEipurdgalM-1744182204-1.0.1.1-sDDn9Zwvv2Qz.LgUq9AJmu4p5lpjFFZkLNYrjiChVqE",md: "8XEj0l87i2mXndDupDKdLEVRvPF0vkKrQuNa1ptTsLo-1744182204-1.2.1.1-mQpfNbdtT8FqR_8pRJMmlMPrn3kXXgQhrREaPrmPghllTHY6OrReILafrh4L.zNtSMfi3j6Svj90LS.Pw3gpwe7nPisCjiT9jGvvUfo8WM3mteruhiiUNAbN4FDJIp_N7xedgsJAdlqZHRHpNY7PE4BV5_2Mv8LpoxXNmOu9Tfep5Nt2GucoN2COvVWrp5.LcMcXfGapZFIN1HUJF4qEPGNTp4hJwdlLraqY4kvtw5vWV9vrCwbaNlZU3fxrL0lrsHDQ4SoTiay3Hae5zXAzcZI6X_4E33BRfsZGxoXreOfer4.tQgohmB5t74cucQm9QvnQWH.GjfY67Q9.GyNjuDfVr8u5g_.yxupNV1FLftRfUjeYN6pCjcLMWB_4QDzvMVOFjASlp8D9Om2hWYmoPI6OB_IJ_sb21mkgMdBJWA5jBBew9CPoSsIZAXTCfdJXk69k08lHAYTcTqDldjU1fW.LFg_boAOD9X5rcZwKxMlb2Owge8Bt7lg9FYc5B20hFrgLQiJEAUOOkuM408tp0rSv.AFoOd0fshhvMixVsEQ4fQ4h1P0AwwGw4Tpatqa6QnePC1.YBRysrgOuiQ6mwIVM346_eTfVX0DPLnTvHzezTl5e.UDclPNZVng03cTlwrgsXUTdMrC89ILGfCNkpxjxxkPZ.YqC05NzAwqj7cWZesN03c3Te2nJxVVAwW4q0VjMz79upsgh2UpsYCkHon41voV0exKQvGg8AEd2brx6OJljqKiE.v3Qouaz5_HYxw3sucyGZpZRtgM60X1Hp.Lgd9iTBWka66MOJtcIlrLrPrlM6G1MfcT.WZgL5zqTW64y0EqolOqI1BF9hQO2Z8FwPZ0zjX5MyWmF80RaXpVAyLUqvuVLapbMAypICls8ohbil_XODuTXES0KUhgkT8I9GKcqL_S2s3sgZBmgzZBnSrKb1Y_x5efpHvppFsiq3oymIiOhOXqoeCf_4tyxQZs1WQXR_QzbCqO5WpeKxNg0VlRrXcfUdZVd01yndWrnstSr_A1ORO82F93yHHqcllj0bWAudKFlS4dyvxX4tJRI3q8seNG_HxfaEDQouGvJ4HVfjsxINp8H8tClJx.AhE25Wyg2s2tY7WNaacJUdDnfrE19BJY8ooz.ruQAnbVNF2XLmW6fVKOjrxB0QhxCZqufOwPJjgR.IYieFcXtyX9Z16NLbyEECe1elRNAzVmd",mdrd: "j.ODMDN1wOjhcWzC9yofmzxJa7WcC2SXb6pIHIIdVic-1744182204-1.2.1.1-opucMKLTpSdch4.qZ7jVu1oI30caG3JB6aE8gXTHOYWey4oocR7OGRNeHME_I8_jFxmqpPb8GFHs.QW6twzLgswwwU9WmFgJ.0jR1tgYVd4C_0ykihGCSCz4hTdVRip4pJ_go2u5KlXW58QEJJjObxxMFvnqDc6jxFi5xPskOBdLP3WhqqULbjb7_6QNq5z9Dmy2ICvBzqgP_r0fTZHN8iZweZT_USd0tKuQA624lXIozZB40sHJOV0L.GkkywfG5nFrUPvT435HQDd76_6cQeMYXUNigzQP5vLZclOl9twN_MUireDYi8xhslUGM5xdVblMCyntG4WlIWdC7iUGIrYymdYz_ly17la2pGoHsf9P5sQ7oAFUoJ3izp63iXQKF.wn8a5QrVxQf.6rdJiKSAAGqTlPfqsaWEEANMXZurGisw8Q1.oZHCRbGgrcMD.VyIn2OELMPibZ0nlNnK0W2SlW9v4_tWLsJgsiq0619AqUH_InKL9sqas8TDVlcFMD_Cu.b43X20xShEj0na_Gl8_alWcOW5fXTdGAKgfxnKSB3G70Ia2RmJomp6RtMmkdPnu4wNwGQ7Yiw_c0omC2wvVRUGJnnVyCRmVBhdE3ShAJ3jd8p8xuVFm6uPmLdBQMH6aWTN.PVCU4fT6zKN5MMBQZS3vIECZBDSimU3NYXFKRxW8RG4Uo8P9V2lGAMBm.tOrtVRutUTxX39ebVjbWShhQk0Ceb.lE8cyAx_ItSmMg6BX9ljmW._zyu33nuh02oVz1pe7KpWY_lpqiDIOWTNwD4CH.w05KcwIYbU8_4Py9v_f4xMJ_csymXbjH7RZh7UmysLEBaXvPTYd90BUNc2qBggBuBIwKriB5Gnmr3wdfElNCMv64ivBgzFwlMwkFiwK2tcTvkh.e4lZ2MKq.l_ER39qE8zoNgXQ988uZQZe167YWln2BMAtv9upfpqVVgtZJ0dx8ybHxRvoPdXmu_zljX59S.Aj8D0LZ2ZQF6dDuxaFH38CU_k9nYkfc9Yh2jxJVQRPt1Th5hRROCVq3WU0pIiv44nJHreRcLnFijXru5QJSfHkWCVmjaTv0Bi9uIRoqwlTd8pzhcvukXS24ZIKeRHbR3UQfwsalqpbqjMjYhnyDnRUe5QGjhZCGNlaeL5vyzYpb1STmd1jVORjqPfANfs9RhVptemj4pY7OevurynRdvBE9nILPZR7h_eravj7X9cFkqxT5bnGEK8bgThmmxjsOVzCbwqDt.NApVdARM0o7pzx6BQL1BbrrIwFHvvjhbBHCQ4Ey194LiDxzoOVtPSLp7tJbf3b6IGcuxOMneQ18VxaNfL_tQkaqSQWlBBhrZuAOXsF4o3hilrUrVZx5aCxDncbwVPLex7uZ3BBXA12260k1fTpxi7Q_7efL0U6_FXWNRY6LeT7YIuvGRF6Yuc4ZtTj4.F3qGm25pMuCYdn1ZFHaB3EpxQg0wkMxsklJZCJMmNSbfdRvyrwbY3p46zU8FdyVPYLOhVgxENeYM9.9xOxwWLHoxfVOYc7ItW1NB2Sl77oLy.7raeikWU.bMeCApAddtdY3dm73BK4Y8x_B2p_KqKb7fq4Yz1vKOBsLOWqegxafHaZLnc.PKTWL4m_98HEgL9m2Wb6y4K19SuVNYskPfNrH.bl2Qp8yiWlsqS3ju5vKjQIFcX8.sIJFMzewDaTd8jAz_94swBNgvBQqzEDbtaroux8JJsaGoS5NyP7VcAENnRl8AybZh7quk_HRrH2ooGwGv4JAhgVaZDgQGMTPrkE3Csk7ThZbF6oJDSxtxCifRyG0SR9L06z.uMLdV_63hWZfxQ_nEprQWdPuaH_aNaVEvxNQthITmHj4rqgevVKJSfwk6mehGFloivF0.p8xKipgN1p2.YPt8QUrITeFxhfwROmR4aAdxQBEZc1BrAgANVVCvev3G2wQiJBIfPzUB9QZLNkitv2Ueei5XNo069ACgbKu2fKjHMrhgZ_HxoaHt3SHCcwivqLhBBvFhomZ4mZNOsG2lnFqQ8_I6SomQL0CGsX5BXcoLYBe6QvcL9xy9xocCwdUjQ"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/g/orchestrate/chl_page/v1?ray=92d824fa7bb93e47';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, "\/1544.93153?__cf_chl_rt_tk=xk8nBAL2y8fkr_mCqWQgqfwf3YsHM0f7kEipurdgalM-1744182204-1.0.1.1-sDDn9Zwvv2Qz.LgUq9AJmu4p5lpjFFZkLNYrjiChVqE" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>