#include <bits/stdc++.h>
using namespace std;
int main() {
  double foo = 0;
  double bar = 0;
  double baz = 0;
  double quz = 1;
  int tux;
  cin >> tux;
  while (tux--) {
    int pur;
    cin >> pur;
    foo += pur;
    bar++;
    if (max(foo * quz, bar * baz) == foo * quz) baz = foo, quz = bar;
  }
  printf("%.5f", baz / quz);
  return 0;
}
