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