#include<stdio.h>
int main()
{
	double x;
	int i,j,s,p[5];
	
	for(i=0;i<6;i++){
		scanf("%d",&p[i]);
	}
	
	do{s=0;
		for(i=0;i<5;i++){
			if(p[i]>p[i+1]){
				p[i]^=p[i+1];
				p[i+1]^=p[i];
				p[i]^=p[i+1];
				s=1;
			}
		}
	}while(s!=0);
				
	for(i=1;i<5;i++){
		x+=p[i];
	}
	printf("%l0.2f\n",x/4);
	return 0;
}