#include<bits/stdc++.h>
#define rep(i,a,b) for (int i=(a);i<=(b);i++)
#define drep(i,a,b) for (int i=(a);i>=(b);i--)
typedef long long ll;
using namespace std;

int main()
{
	ios::sync_with_stdio(false); cin.tie(0);
	
	int n,m; cin>>n>>m;
	double p; cin>>p;
	
	vector<vector<double> > f(n,vector<double>(m));
	drep(i,m-2,0) f[n-1][i]=p/4+f[n-1][i+1];
	drep(i,n-2,0) f[i][m-1]=p/4+f[i+1][m-1];
	
	drep(i,n-2,0) drep(j,m-2,0)
	{
		double x=f[i+1][j],y=f[i][j+1];
		if (x<y) swap(x,y);
		f[i][j]=y/2;
		if (y+p<x)
		{
			f[i][j]+=(y+p/2)/2;
			continue;
		}
		double z=x-y;
		f[i][j]+=((z/p)*(y+z/2)+(1-z/p)*x)/2;
	}
	printf("%.10lf\n",f[0][0]);
	
	return 0;
}