#include <bits/stdc++.h>
using namespace std;
inline int read() {
  int x = 0, f = 1;
  char ch = getchar();
  while (ch < '0' || ch > '9') {
    if (ch == '-') f = -1;
    ch = getchar();
  }
  while (ch >= '0' && ch <= '9') {
    x = (x << 1) + (x << 3) + (ch ^ 48);
    ch = getchar();
  }
  return x * f;
}
long long n, k;
int main() {
  n = read(), k = read();
  long long p = (sqrt((n + k) * 8 + 9) - 3) / 2;
  printf("%lld\n", p * (p + 1) / 2 - k);
  return 0;
}
