#include <bits/stdc++.h>
using namespace std;
double n, m, x, y, a, b = 1;
int main() {
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> m;
    x = m + x;
    y++;
    if (x * b > a * y) {
      a = x;
      b = y;
    }
  }
  printf("%.6lf", a * 1.0 / b);
  return 0;
}
