#include<iostream>
using namespace std;
int main(){
    double n,m;
    cin>>n>>m;
    double p;cin>>p;
    double ans=0.0;
    if (n>m)swap(n,m);
    if (n==1){
        if (m==1){
            cout<<p<<endl;
            return 0;
        }
        ans+=2*p*p;
        ans+=(m-2)*p*p*p;
        cout<<ans<<endl;
        return 0;
    }
    ans+=4*p*p*p;
    ans+=(n+m-4)*p*p*p*p;
    ans+=(n-2)*(m-2)*p*p*p*p*p;
    cout<<ans<<endl;
    return 0;
}