#include <bits/stdc++.h>
#define FOR(i,a,b) for(int i = (a); i < (b); ++i)
#define REP(i,n) for(int i = 0; i < (n); ++i)
using namespace std;
typedef long long ll;
const int INF = 1e9;
const double PI = acos(-1.0);

int main(void) {
	cin.tie(0);
	ios::sync_with_stdio(false);
	
	int s[6];
	
	REP(i, 6) cin >> s[i];
	
	sort(s, s+6);
	
	int sum = 0;
	REP(i, 4) sum += s[i + 1];
	
	cout << fixed << setprecision(2) << (double) sum / 4;
	
	return 0;
}