#include <bits/stdc++.h>

using namespace std;

const double PI = acos(-1.0);

int main() {
    int a[3];
    cin >> a[0] >> a[1] >> a[2];
    cout << fixed << setprecision(3) << std::accumulate(a, a + 3, 0) / 3.0;
    return 0;
}