#include <iostream>
#include <algorithm>
#include <iomanip>
using namespace std;
int n, s, v[1005];
int main()
{
cin >> n;
for(int i = 1; i <= n; i++) cin >> v[i];
cout << setprecision(3) << accumulate(v + 1, v + n + 1, 0, [] (int x, int a) { return ~a & 1 ? s++, x + a : x; }) / (float)s;
}