#include <bits/stdc++.h>
using namespace std;
using ld = long double;
int main(){
    ld n,m,p;
    cin>>n>>m>>p;
    ld tn=n==1?1:(p*(n-2)+2)*p,tm=m==1?1:(p*(m-2)+2)*p;
    cout<<fixed<<setprecision(15)<<(tn*tm*p)<<endl;
}