#include<iostream>
#include<cstdio>
#include<cmath>
using  namespace std;
int main ()
{
    double a,b,c;
    double ans1=0.0,ans2=0.0;
    double r,p;
    cin>>a>>b>>c;
    r=a+b;
    r=r*r;
    r*=2;
    r=sqrt(r);
    p=a;
    p=p*p;
    p*=2;
    p=sqrt(p);
    ans1=r*p;
    r=c+b;
    r=r*r;
    r*=2;
    r=sqrt(r);
    p=c;
    p=p*p;
    p*=2;
    p=sqrt(p);
    ans2=r*p;
    double ans=min(ans1,ans2);
    int c1,c2,c3,c4,c5,c6;
    c6=int (ans);
    ans-=c6;
    int h;
    ans*=10000;
    h=int(ans);
    c1=h/10000;h=h%10000;
    c2=h/1000;h=h%1000;
    c3=h/100;h=h%100;
    c4=h/10;h=h%10;
    c5=h;
     if(c5>4)c4++;
     if(c4>9){c4=0;c3++;}
     if(c3>9){c3=0;c2++;}
     if(c2>9){c2=0;c1++;}
     if(c1>9){c1=0;c6++;}
     cout<<c6<<"."<<c1<<c2<<c3<<c4<<endl;
}
