#include <iostream>
#include <algorithm>
#include <cmath>
using namespace std;

int main() {
    int p, t, g1, g2, g3, gj;
    while(cin >> p >> t >> g1 >> g2 >> g3 >> gj)
    {
        if(abs(g1 - g2) <= t) 
            printf("%.1lf\n",(double)(g1 + g2) / 2);
        else if(abs(g1 - g3) <= t && abs(g2 - g3))
            printf("%.1lf\n",(double)(g1 + g2 + g3) / 3);
        else if(abs(g1 - g3) <= t)
            printf("%.1lf\n",(double)(g1 + g3) / 2);
        else if(abs(g2 - g3) <= t)
            printf("%.1lf\n",(double)(g2 + g3) / 2);
        else printf("%.1lf\n", (double) gj);
    }
    return 0;
}
// 64 位输出请用 printf("%lld")