x,y,n,k,i,j,p,q,r,s,a[1000];
c(int*a,int*b){return*a-*b;}
main(){
	for(;~scanf("%d",a+i);i++);
	qsort(a,6,4,c);
	n=!printf("%.2f",(a[1]+a[2]+a[3]+a[4])/4.);
}