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