#include <bits/stdc++.h>
int main() {
  int i, n, k;
  int timeleft, timetaken = 0, probsolved = 0;
  scanf("%d %d", &n, &k);
  timeleft = 240 - k;
  for (i = 1; i <= n; i++) {
    timetaken += (5 * i);
    if (timeleft - timetaken < 0)
      break;
    else {
      probsolved += 1;
      if (probsolved == n) break;
    }
  }
  printf("%d", probsolved);
  return 0;
}
