#include <bits/stdc++.h>
using namespace std;
int main() {
  int tux;
  cin >> tux;
  int foo = 0, bar = 0, baz = 0, quz = 1;
  for (; tux > 0; tux--) {
    int pur;
    cin >> pur;
    foo += pur;
    bar += 1;
    int pr1 = foo * quz;
    int pr2 = bar * baz;
    int pr3 = foo * quz;
    if (max(pr1, pr2) == pr3) {
      baz = foo;
      quz = bar;
    }
  }
  double ans = (double)((double)baz / quz);
  printf("%.6lf\n", ans);
  return 0;
}
