题解

#include<bits/stdc++.h>
#define ll long long                                                                  //防抄袭标记
#define MAXN 100005
#define maxn 1000005
#define MAXM 10000005
#define maxm 100000005
using namespace std;
int a[MAXN],b;
int main(){
	for(int i = 1;i<=4;i++){
		cin>>a[i];
	}
	sort(a+1,a+5);
	printf("%.2lf",(a[2]+a[3])*1.0/2);
	return 0;
}