#include <cmath>
#include <vector>
#include <iostream>
using namespace std;
int main() {
	int N, M; double P;
	cin >> N >> M >> P;
	vector<long long> ways(6);
	if (N > M) swap(N, M);
	if (N == 1 && M == 1) {
		ways[1] = 1;
	}
	else if (N == 1) {
		ways[2] = 2;
		ways[3] = M - 2;
	}
	else {
		ways[3] = 4;
		ways[4] = 2LL * (N + M) - 8;
		ways[5] = 1LL * N * M - ways[3] - ways[4];
	}
	double ans = 0.0;
	for (int i = 1; i <= 5; ++i) {
		ans += ways[i] * pow(P, i);
	}
	cout.precision(15);
	cout << ans << endl;
	return 0;
}