#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>
#include <cmath>
#include <bitset>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <algorithm>
#include <complex>
#include <unordered_map>
#include <unordered_set>
#include <random>
#include <cassert>
#include <fstream>
#include <utility>
#include <functional>
#include <time.h>
#include <stack>
#include <array>
#define popcount __builtin_popcount
using namespace std;
typedef long long int ll;
typedef pair<int, int> P;

int main()
{
	ll n, m;
	cin>>n>>m;
	double p;
	cin>>p;
	double ans=0;
	if(n>=2 && m>=2){
		ans=4*p*p*p+(n-2)*2*p*p*p*p+(m-2)*2*p*p*p*p+(n-2)*(m-2)*p*p*p*p*p;
	}else if(n==1 && m==1){
		ans=p;
	}else if(n==1){
		ans=2*p*p+(m-2)*p*p*p;
	}else{
		swap(n, m);
		ans=2*p*p+(m-2)*p*p*p;
	}
	printf("%.7lf\n", ans);
	return 0;
}