#include <bits/stdc++.h>
using namespace std;
template<typename T1,typename T2> inline void chmin(T1 &a,T2 b){if(a>b) a=b;}
template<typename T1,typename T2> inline void chmax(T1 &a,T2 b){if(a<b) a=b;}
using Int = long long;
const char newl = '\n';


struct Precision{
  Precision(){
    cout<<fixed<<setprecision(12);
  }
}precision_beet;


template<typename T> void drop(const T &x){cout<<x<<endl;exit(0);}

//INSERT ABOVE HERE
signed main(){
  cin.tie(0);
  ios::sync_with_stdio(0);

  int n,m;
  cin>>n>>m;
  using D = double;
  D p;
  cin>>p;
  if(n>m) swap(n,m);
  if(n==1){
    if(m==1) drop(p);
    drop(p*p+p*p*p*(m-2)+p*p);
  }
  D ans=0;
  ans+=p*p*p*4;
  ans+=p*p*p*p*((n-2)*2+(m-2)*2);
  ans+=p*p*p*p*p*(n-2)*(m-2);
  drop(ans);
  return 0;
}