#include<iostream>
#include<iomanip>
#include<cassert>
using namespace std;
int H,W;
long double dp[1010][1010];
int P;
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cin>>H>>W>>P;
	dp[H-1][W-1]=0;
	for(int i=H-1;i>=0;i--)for(int j=W-1;j>=0;j--)
	{
		if(i==H-1&&j==W-1)continue;
		if(i==H-1)
		{
			dp[i][j]=dp[i][j+1]+1/(long double)4;
		}
		else if(j==W-1)
		{
			dp[i][j]=dp[i+1][j]+1/(long double)4;
		}
		else
		{
			dp[i][j]=0;
			long double x=dp[i+1][j],y=dp[i][j+1];
			for(int _=0;_<2;_++)
			{
				if(y<=x)
				{
					dp[i][j]+=y/2;
				}
				else if(x+1<=y)
				{
					dp[i][j]+=x/2+1/(long double)4;
				}
				else
				{
					long double d=y-x;
					dp[i][j]+=d*(d/2+x)/2;
					dp[i][j]+=(1-d)*y/2;
				}
				swap(x,y);
			}
		}
	}
	cout<<fixed<<setprecision(16)<<dp[0][0]*P<<endl;
}