A 讀題題

B 就是你排名第p，得了x分，而最終至少需要y分，你需要最少的successful hack，使得最終得分s>=y，且由s隨機取25個數，使p被選中。

（1）暴力枚舉hack成功幾次，失敗幾次就好了

（2）另解：枚舉盡可能小的s，使|s-x|=0(mod 50),分類討論

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 一看到題就打了exgcd，調了一晚上，各種看錯，最後發現爆long long了。。

其實列個不等式解就好了

VK Cup 2017 Round 3 + Codeforces Round #412