#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < n; ++i)
using ll = long long;
using namespace std;
const int INF = 1e9;

int main() {
    int a[6];
    rep(i, 6) cin >> a[i];

    sort(a, a + 6);

    int sum = 0;
    rep(i, 4)
        sum += a[i + 1];

    printf("%.2f\n", sum / 4.0);

    return 0;
}