#include <bits/stdc++.h>
using namespace std;
int main() {
  double t, f = 0, br = 0, bz = 0, qz = 1;
  cin >> t;
  for (int i = 1; i <= t; i++) {
    double PUR;
    cin >> PUR;
    f = f + PUR;
    br = br + 1;
    if (f * qz > bz * br) {
      bz = f;
      qz = br;
    }
  }
  double a;
  a = bz / qz;
  cout << a;
  return 0;
}
