#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int n;
int k;
int buscaBinaria() {
  int inf = 0;
  int sup = n;
  while (sup - inf > 1) {
    int mid = (sup + inf) / 2;
    int tempo = 0;
    for (int i = 0; i <= mid; ++i) {
      tempo += i * 5;
    }
    if (tempo > k)
      sup = mid;
    else if (tempo < k)
      inf = mid;
    else
      inf = mid;
  }
  int tempo = 0;
  for (int i = 0; i <= sup; ++i) tempo += i * 5;
  if (tempo <= k) return sup;
  return inf;
}
int main() {
  scanf("%d %d", &n, &k);
  k = 60 * 4 - k;
  printf("%d\n", buscaBinaria());
  return 0;
}
