#include <bits/stdc++.h>
#pragma comment(linker, "/stack:256000000")
using namespace std;
int main() {
  int tux;
  cin >> tux;
  int foo = 0;
  int bar = 0;
  int baz = 0;
  int quz = 1;
  for (int i = 0; i < tux; i++) {
    int pur;
    cin >> pur;
    foo = foo + pur;
    bar = bar + 1;
    if (max(foo * quz, bar * baz) == foo * quz) {
      baz = foo;
      quz = bar;
    }
  }
  printf("%.10lf\n", (double)baz / quz);
  return 0;
}
