#include <bits/stdc++.h>
using namespace std;
bool test(long long, long long, long long);
int main(void) {
  long long n, m;
  cin >> n >> m;
  long long first, last;
  first = 0;
  last = sqrt(2 * n) + 1;
  if (m >= n) {
    cout << n;
    return 0;
  }
  while (test(first, n, m) == 0) {
    long long med;
    med = (first + last) / 2;
    if (test(med, n, m) == 1)
      last = med;
    else
      first = med;
    if (last - first == 1 && test(first, n, m) == 0) first = last;
  }
  cout << first + m;
  return 0;
}
bool test(long long day, long long n, long long m) {
  if (day % 2 == 0) {
    if ((day / 2) * (day + 1) >= (n - m)) return 1;
  } else {
    if (day * ((day + 1) / 2) >= (n - m)) return 1;
  }
  return 0;
}
