#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")