#include<iostream>
#include<cstdio>
#include<cmath>
using namespace std;

double a,b,c;

int main()
{
    scanf("%lf%lf%lf",&a,&b,&c);
    if(fabs(a-c)>1e-3){printf("0\n");return 0;}
    printf("%.4lf\n",a*(a+b)*2);
}
