#include <bits/stdc++.h>   using namespace std;   int main() {     long long N;     scanf( %I64d , &N);     int l = 1, r = 20000000, ans = 0;     while (l <= r) {       int mid = (l + r) >> 1;       if ((long long)mid * (mid + 1) < N * 2)         ans = mid, l = mid + 1;       else         r = mid - 1;     }     printf( %I64d , N - (long long)ans * (ans + 1) / 2);     return 0;   }   