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

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

    long double nn = (long double)n;
    long double mm = (long double)m;
    long double ans;
    if (n == 1) {
        if (m == 1) ans = p;
        else ans = (2.0 + p*(mm-2));
    } else {
        ans = p*p*p*(4.0 + (2.0*mm+2.0*nn-8.0)*p + p*p*(mm-2.0)*(nn-2.0));
    }
    printf("%.10Lf\n", ans);
    return 0;
}