#include<bits/stdc++.h>
int main(){
    int n,m;std::cin>>n>>m;
    double p;std::cin>>p;
    if(n>m)std::swap(n,m);
    std::cout<<std::setprecision(10)<<(n==1
        ?2*p*p+(m-2)*p*p*p
        :4*p*p*p+(2*n+2*m-8)*p*p*p*p+(n-2)*(m-2)*p*p*p*p*p
        )<<std::endl;
}