#include <bits/stdc++.h>
using namespace std;

int main()
{
    int n, m; cin >> n >> m;
    double p; cin >> p;
    if (n > m) swap(n, m);

    double ans;
    if (n == 1) {
        if (m == 1) ans = p;
        else ans = p*p*(2.0 + p*(m-2));
    } else {
        ans = p*p*p*(4.0 + p*(2*m+2*n-8) + p*p*(m-2)*(n-2));
    }
    printf("%.10f\n", ans);
    return 0;
}