#include <bits/stdc++.h>

using namespace std;

using ll = long long;



int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int n, m;
    double p;
    cin >> n >> m >> p;
    if (n > m) swap(n, m);
    
    double ans = 0;
    if (m == 1) {
        // n == 1 && m == 1
        ans = p;
    } else if (n == 1) {
        ans = p * (2 + p * (m - 2));
        ans *= p;
    } else {
        ll rest = n;
        rest *= m;
        rest -= 2 * (n + m) - 4;
        ans = p * p * (4 + p * (2 * (n + m - 4) + p * rest));
        ans *= p;
    }
    cout << fixed << setprecision(20) << ans << "\n";
    return 0;
}