#include <bits/stdc++.h>
using namespace std;
int main() {
  long long i, j, n, m, k, it, it1, l, r, mini, ext, next, ans;
  scanf("%lld %lld %lld", &n, &m, &k);
  ans = 1;
  m -= n;
  l = k;
  r = k;
  k = 1;
  while (m) {
    if (l == 1 && r == n) {
      ans += (m / k);
      break;
    }
    if (m >= k) {
      m -= k;
      ans++;
      if (l > 1) {
        l--;
        k++;
      }
      if (r < n) {
        r++;
        k++;
      }
    } else
      break;
  }
  printf("%lld\n", ans);
  return 0;
}
