#include <bits/stdc++.h>
using namespace std;
const double pi = acos(-1.0);
int tux;
void solve() {
  int foo = 0;
  int bar = 0;
  int baz = 0;
  int quz = 1;
  for (int i = 0; i < tux; i++) {
    int pur;
    cin >> pur;
    foo += pur;
    bar++;
    if (max(foo * quz, bar * baz) == foo * quz) {
      baz = foo;
      quz = bar;
    }
  }
  cout << baz * 1. / quz << endl;
}
int main() {
  while (cin >> tux) {
    solve();
  }
}
