#include <bits/stdc++.h>
using namespace std;
typedef pair<int,int> pii;
typedef long long ll;
#define ITR(i,c) for(auto i=begin(c);i!=end(c);i++)
#define FORE(x,arr) for(auto &x:arr)
#define FOR(i,a,n) for(int i=a;i<(int)(n);i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(c) begin(c),end(c)
const int DX[4]={0,1,0,-1}, DY[4]={-1,0,1,0};
const int INF = 1e9;

int main(int argc, char const *argv[]) {
    int s[6];
    REP(i,6) {cin >> s[i];}
    sort(ALL(s));
    double sum = s[1]+s[2]+s[3]+s[4];
    printf("%f\n",sum/4);
    return 0;
}