#include <algorithm>
#include <iostream>
#include <iomanip>
#include <map>
#include <numeric>
#include <set>
#include <sstream>
#include <string>
#include <vector>
#include <cmath>
using namespace std;

#define FOR(i,s,e) for (int i = int(s); i != int(e); i++)
#define FORIT(i,c) for (typeof((c).begin()) i = (c).begin(); i != (c).end(); i++)
#define ISEQ(c) (c).begin(), (c).end()



int main(){
	int S[6];
	FOR(i,0,6) cin >> S[i];
	sort(S,S+6);
	double ans = (double)(S[1]+S[2]+S[3]+S[4])/4;
	printf("%.2f\n", ans);
	return 0;
}