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来源:codeforces E. Tetrahedron 来源:codeforces E. Tetrahedron You are given a tetrahedron. Let's mark its vertices with letters A, B, C and D correspondin 阅读全文
摘要:
来源:codeforces D. Timetable Ivan is a student at Berland State University (BSU). There are n days in Berland week, and each of these days Ivan might ha 阅读全文