// #pragma GCC optimize("O3,unroll-loops")
#include <bits/stdc++.h>
// #include <x86intrin.h>
using namespace std;
#if __cplusplus >= 202002L
using namespace numbers;
#endif



int main(){
	cin.tie(0)->sync_with_stdio(0);
	cin.exceptions(ios::badbit | ios::failbit);
	cout << fixed << setprecision(15);
	int nr, nc, p;
	cin >> nr >> nc >> p;
	vector dp(nr, vector<double>(nc));
	for(auto x = nr - 1; x >= 0; -- x){
		for(auto y = x == nr - 1 ? nc - 2 : nc - 1; y >= 0; -- y){
			if(x + 1 >= nr){
				dp[x][y] = dp[x][y + 1] + p / 4.0;
			}
			else if(y + 1 >= nc){
				dp[x][y] = dp[x + 1][y] + p / 4.0;
			}
			else{
				double a = dp[x + 1][y], b = dp[x][y + 1];
				if(a >= b + p){
					dp[x][y] += (p + 2 * b) / 2 * p;
				}
				else if(a <= b){
					dp[x][y] += a * p;
				}
				else{
					dp[x][y] += (p + 2 * b) / 2 * p - (p + b - a) * (p + b - a) / 2;
				}
				if(b >= a + p){
					dp[x][y] += (p + 2 * a) / 2 * p;
				}
				else if(b <= a){
					dp[x][y] += b * p;
				}
				else{
					dp[x][y] += (p + 2 * a) / 2 * p - (p + a - b) * (p + a - b) / 2;
				}
				dp[x][y] /= 2 * p;
			}
		}
	}
	cout << dp[0][0] << "\n";
	return 0;
}

/*

*/