#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k, time = 60 * 4;
  int a = 0, cnt = 0;
  cin >> n >> k;
  while (a <= time - k && cnt <= n) {
    cnt++;
    a += cnt * 5;
  }
  (cnt > n) ? cout << n : cout << cnt - 1;
  return 0;
}
