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