#include <bits/stdc++.h>
using namespace std;
int main() {
  int t;
  int a = 0, b = 0, c = 0, d = 1;
  int tt;
  cin >> t;
  while (t--) {
    cin >> tt;
    a += tt;
    b++;
    if (a * d > b * c) {
      c = a;
      d = b;
    }
  }
  cout << c * 1.000000 / d << endl;
  return 0;
}
