#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(int)(n);i++)
using namespace std;
using ll = long long ;
using P = pair<int,int> ;
using pll = pair<long long,long long>;
constexpr int INF = 1e9;
constexpr long long LINF = 1e17;
constexpr int MOD = 1000000007;
constexpr double PI = 3.14159265358979323846;

int main(){
    ll n,m;
    cin >> n >> m;
    if(n > m) swap(n,m);
    double p;
    cin >> p;
    double ans = 0;
    if(n==1&&m==1){
        ans = p;
    }else if(n==1){
        ans = 2*p*p + (m-2)*p*p*p;
    }else{
        ans = 4*p*p*p;
        ans += 2*(n-2)*p*p*p*p;
        ans += 2*(m-2)*p*p*p*p;
        ans += (double)(n-2)*(double)(m-2)*p*p*p*p*p;
    }
    cout << setprecision(20) << ans << endl;
    return 0;
}