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

int main() {
	int64_t n, m; cin >> n >> m;
	double p; cin >> p;
	double ans = 0;
	ans += 4 * p * pow(p, 2);
	ans += (2 * (n - 2) + 2 * (m - 2)) * p * pow(p, 3);
	ans += (n * m - (2 * n + 2 * m - 4)) * p * pow(p, 4);
	printf("%.15f\n", ans);
	return 0;
}