func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     long long n, k;     cin >> n >> k;     long long l = 1, u = n, mid;     while (l <= u) {       mid = (l + u) / 2;       long long sum = (mid * (mid + 1)) / 2;       sum = sum - (n - mid);       if (sum == k) {         cout << n - mid << endl;         break;       } else if (sum < k) {         l = mid + 1;       } else         u = mid - 1;     }     return 0;   }   