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