#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  int64_t n, m;
  cin >> n >> m;
  if (n <= m) {
    cout << n << endl;
  } else {
    n -= m;
    int64_t l = 0, r = 2e9;
    while (l < r) {
      int64_t m = (l + r) / 2;
      int64_t val = m * (m + 1) / 2;
      if (val >= n) {
        r = m;
      } else {
        l = m + 1;
      }
    }
    cout << l + m << endl;
  }
  return 0;
}
