#include <iostream>
//#include<cstdio>
#include<cmath>
using namespace std;

int main() {
    double p,t,g1,g2,g3,gj;
    while (cin >> p>>t>>g1>>g2>>g3>>gj) { 
        double score;
        if(fabs(g1-g2)<=t)score=(g1+g2)/2.0;
        else{
            if((fabs(g3-g1)<=t||fabs(g3-g2)<=t)&&(!(fabs(g3-g1)<=t&&fabs(g3-g2)<=t)))
            {
                int min=fabs(g3-g1);
                int x=g1;
                if(min>=fabs(g3-g2))x=g2;
                score=(x+g3)/2.0;
            }
            else if((fabs(g3-g1)<=t&&fabs(g3-g2)<=t)){
                double score1=max(g1,g2);
                score=max(score1,g3);
            }
            else if(fabs(g3-g1)>t&&fabs(g3-g2)>t){
                score=gj;
            }
        }
        printf("%.1f",score);
    }
}