#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int tux;
  cin >> tux;
  int foo = 0;
  int bar = 0;
  int baz = 0;
  int quz = 1;
  while (tux--) {
    int pur;
    cin >> pur;
    foo += pur;
    bar += 1;
    if (max(foo * quz, bar * baz) == foo * quz) {
      baz = foo;
      quz = bar;
    }
  }
  double ans = (double)baz / quz;
  cout << fixed << setprecision(5) << ans << '\n';
  return 0;
}
