12行轻松过

#include <iostream>
#include <iomanip>
#include <algorithm>
using namespace std;

int main(){
    int a[4];
    cin >> a[0] >> a[1] >> a[2] >> a[3];
    sort (a, a+4);
    cout << fixed << setprecision(2) << (a[1]+a[2])/2.0 << endl;
    return 0;
}