#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
  long long n, k;
  cin >> n >> k;
  long long l = 0;
  long long r = n;
  while (l != r) {
    long long mid = (l + r) / 2;
    if (mid * (mid + 1) / 2 - (n - mid) < k)
      l = mid + 1;
    else
      r = mid;
  }
  cout << n - l;
  return 0;
}
