#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;}