摘要：World Cup NoiseTime Limit:1000MSMemory Limit:30000KTotal Submissions:13155Accepted:6512DescriptionBackground"KO-RE-A, KO-RE-A" shout 54.000 happy football fans after their team has reached the semifinals of the FIFA World Cup in their home country. But although their excitement is real, th 阅读全文

摘要：Farey SequenceTime Limit:1000MSMemory Limit:65536KTotal Submissions:9180Accepted:3501DescriptionThe Farey Sequence Fn for any integer n with n >= 2 is the set of irreducible rational numbers a/b with 0 < a < b <= n and gcd(a,b) = 1 arranged in increasing order. The first few areF2 = {1/2 阅读全文

摘要：RelativesTime Limit:1000MSMemory Limit:65536KTotal Submissions:8841Accepted:4134DescriptionGiven n, a positive integer, how many positive integers less than n are relatively prime to n? Two integers a and b are relatively prime if there are no integers x > 1, y > 0, z > 0 such that a = xy a 阅读全文