#include<stdio.h>
int main()
{
	long long int n, m;
	scanf("%lld %lld", &n, &m);
	double p;
	scanf("%lf", &p);
	double ans;
	if (n == 1 && m == 1)
		ans = p;
	else if (n == 1)
		ans = 2 * p * p + (m - 2) * p * p * p;
	else if (m == 1)
		ans = 2 * p * p + (n - 2) * p * p * p;
	else
		ans = 4 * p * p * p + 2 * (n + m - 4) * p * p * p * p + (n - 2) * (m - 2) * p * p * p * p * p;
	printf("%.20lf\n", ans);
	return 0;
}