#include <bits/stdc++.h>
int biggr(int a, int b) {
  if (a > b) return a;
  return b;
}
int main() {
  int n, foo = 0, bar = 0, baz = 0, quz = 0, pur;
  scanf("%d", &n);
  while (n--) {
    scanf("%d", &pur);
    foo += pur;
    bar++;
    if (biggr(foo * quz, bar * baz) == foo * quz) {
      baz = foo;
      quz = bar;
    }
  }
  printf("%.6f\n", (double)baz / quz);
  return 0;
}
