#include<bits/stdc++.h>

using namespace std;
const int N = 1e3+7;

double f[N][N], pw2[N*2];

int main() {
	double P, r, c;
	pw2[0] = 1.0;
	for(int i = 1; i <= 2002; i++) 
		pw2[i] = pw2[i - 1] * 0.50;
	cin >> r >> c >> P;
	
	for(int i = r; i >= 1; i--) {
		for(int j = c; j >= 1; j--) {
			if(i == r && j == c) continue;
			if(i == r) {
				f[i][j] = f[i][j + 1] + P * pw2[2];	
			}
			else if(j == c) {
				f[i][j] = f[i + 1][j] + P * pw2[2];	
			}
			
			else {
				//f[i][j] = pw2[1] * min(f[i + 1][j], f[i][j + 1] + P * pw2[1])
				//	+ pw2[1] * min(f[i][j + 1], f[i + 1][j] + P * pw2[1]);	
				double fx = f[i + 1][j], fy = f[i][j + 1];
				if(fx > fy) swap(fx, fy);
				
				if(fy >= fx + P) {
					f[i][j] = fx + P * pw2[2];	
				} else {
					f[i][j] = (P - fy + fx) * fy / (2*P) + fx / 2 + (fy - fx) * (fx + fy) / (4*P);	
				}
				
			}
		}
	}
	
	
	
	printf("%.8lf", f[1][1]);	
return 0;	
}