#include <stdio.h>

int main() {
	double p;
	int n, m, tmp;
	scanf("%d%d%lf", &n, &m, &p);
	if (n > m) {
		tmp = n;
		n = m;
		m = tmp;
	}
	if (n == 1) {
		if (m == 1) printf("%.20lf\n", p);
		else printf("%.20lf\n", (m - 2) * p * p * p + p * p * 2);
	}
	else {
		printf("%.20lf\n", p * p * p * 4 + p * p * p * p * (n - 2 + m - 2) * 2 + p * p * p * p * p * (n - 2) * (m - 2));
	}
}