#include <iostream.h>
#include <math.h>
#include <stdio.h>
#include <vector>
#include <queue>
#include <string.h>
#include <stack>

using namespace std;

double p,q,r;
double a,s;

int main(){
    cin>>p>>q>>r;
    //cout<<p<<" "<<q<<" "<<r<<endl;
    if(p!=r){
        cout<<0<<endl;
    }
    else{
        a=2*p;
        s+=(a*p)/2;
        s+=(a*q);
        s+=(a*r)/2;
        printf("%.4f\n",s);
    }
	return 0;
}
