#define _USE_MATH_DEFINES
#include <algorithm>
#include <bitset>
#include <cstdio>
#include <functional>
#include <iostream>
#include <cfloat>
#include <climits>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <time.h>
#include <vector>
#include <random>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;
typedef pair<ll, int> ll_i;
typedef pair<double, int> d_i;
typedef pair<ll, ll> ll_ll;
typedef pair<double, double> d_d;
struct edge { int u, v; ll w; };
typedef vector<vector<bool> > grid;

ll INF = LLONG_MAX / 3;
ll MOD = 1000000007;
ll _MOD = 1000000009;
double EPS = 1e-10;

int main() {
	vector<int> a(6);
	for (int& x: a) cin >> x;
	sort(a.begin(), a.end());
	int sum = 0;
	for (int i = 1; i <= 4; i++)
		sum += a[i];
	printf("%.2f\n", sum / 4.0);
}