#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, t, s = 0, i;
  cin >> n >> t;
  t = 240 - t;
  for (i = 1; (s + 5 * i <= t) && i <= n; ++i) {
    s += 5 * (i);
  }
  cout << i - 1;
}
