#include<bits/stdc++.h>
#define LL long long
using namespace std;
double f[1005][1005],p;
double calc(double h,double l){
	if(h<=l) return h;
	else if(h>=l+p) return l+p/2.0;
	const double bound=h-l;
	return (l+bound/2)*bound/p+h*(p-bound)/p;
}
signed main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	int n,m;
	cin>>n>>m>>p;
	for(int i=1;i<=m;i++) f[n+1][i]=1e1000;
	for(int i=1;i<=n;i++) f[i][m+1]=1e1000;
	for(int i=n;i>=1;i--)
	for(int j=m;j>=1;j--){
		if(i==n&&j==m) continue;
		f[i][j]=(calc(f[i][j+1],f[i+1][j])+calc(f[i+1][j],f[i][j+1]))/2;
	}
	printf("%.10lf",f[1][1]);
	return 0;
}