1

#include <bits/stdc++.h>
using namespace std;
int main()
{
int sum=0,a,b,c,d,max=0,min=0;
double jun=0;
cin>>a>>b>>c>>d;
if(a>=b&&a>=c&&a>=d)
{
max=a;
}
else if(b>=a&&b>=c&&b>=d)
{
max=b;
}
else if(c>=a&&c>=b&&c>=d)
{
max=c;
}
else if(d>=a&&d>=b&&d>=c)
{
max=d;
}

if(a<=b&&a<=c&&a<=d)
{
    min=a;
}
else if(b<=a&&b<=c&&b<=d)
{
    min=b;
}
else if(c<=a&&c<=b&&c<=d)
{
    min=c;
}
else if(d<=a&&d<=b&&d<=c)
{
    min=d;
}
sum=(a+b+c+d)-(min+max);
jun=sum/2.0;
printf("%.02f",jun);
return 0;

}