#include<iostream>
#include<algorithm>
#include<cmath>
using namespace std;
double p,q,r,ch=0.00000001;
struct pal
{
    double x,y;
};
pal a,b,c,d;
void read()
{
    cin>>p>>q>>r;
    a.x=0;
    a.y=0;
    b.x=p;
    b.y=0;
    c.x=p+q;
    c.y=0;
    d.x=p+q+r;
    d.y=0;
}
int main()
{
    int i,j,t,l=0;
    double d1,d2,d3,d4,sq;
    int sq1;
    read();
    if(p+q!=r+q)
    {
        cout<<0<<endl;
        return 0;
    }
    else
    {
        int asd;
        asd=(q+r)*p;
        asd*=2;
        printf("%d",asd);
        printf(".0000");
    }
    return 0;
}
