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