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