#include <bits/stdc++.h>   using namespace std;   long long n, root, val, rem;   int main() {     cin >> n;     root = floor((sqrt(1.0 + 8.0 * n) - 1.0) / 2.0);     val = root * (root + 1) / 2;     if (n == val) --root;     val = root * (root + 1) / 2;     rem = n - val;     cout << rem << endl;     return 0;   }   