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

int main() {
    long n, m;
    double p;
    cin >> n >> m >> p;
    if (n > m) swap(n, m);
    cout << setprecision(17);
    if (m == 1) {
        cout << p << endl;
    } else if (n == 1) {
        cout << 2 * p * p + (m - 2) * p * p * p << endl;
    } else {
        cout << 4 * p * p * p + 2 * (m - 2 + n - 2) * p * p * p * p + (m - 2) * (n - 2) * p * p * p * p * p << endl;
    }
}