A 读题题
B 就是你排名第p，得了x分，而最终至少需要y分，你需要最少的successful hack，使得最终得分s>=y，且由s随机取25个数，使p被选中。
（1）暴力枚举hack成功几次，失败几次就好了
（2）另解：枚举尽可能小的s，使|s-x|=0(mod 50),分类讨论
If s?≤?x, we need 0 successful hacks, since we can just make (x?-?s)?/?50 unsuccessful hacks.
If s?>?x and s?-?x is divisible by 100, we need exactly (s?-?x)?/?100 successful hacks.
If s?>?x and s?-?x is not divisible by 100, we need (s?-?x?+?50)?/?100 successful hacks and one unsuccessful hack.
C 一看到题就打了exgcd，调了一晚上，各种看错，最后发现爆long long了。。
其实列个不等式解就好了
VK Cup 2017 Round 3 + Codeforces Round #412
原文：http://www.cnblogs.com/supy/p/6911295.html