# include <bits/stdc++.h>

const int N=100010,INF=0x3f3f3f3f;

inline int read(void){
	int res,f=1;
	char c;
	while((c=getchar())<'0'||c>'9')
		if(c=='-') f=-1;
	res=c-48;
	while((c=getchar())>='0'&&c<='9')
		res=res*10+c-48;
	return res*f;
}

int n,m;
double p;
double f[1010][1010];

double rinf=1e14;

int main(void){
	n=read(),m=read(),p=read();
	
	for(int i=1;i<=n+1;++i) for(int j=1;j<=m+1;++j) f[i][j]=rinf;
	
	for(int i=n;i;--i){
		for(int j=m;j;--j){
			if(i==n&&j==m){
				f[i][j]=0;
				continue;
			}
			double A=f[i][j+1],B=f[i+1][j];
			f[i][j]=0;
			double lim=std::max(A-B,0.0);
			lim=std::min(lim,p);			
			f[i][j]+=(B*lim+0.5*lim*lim+A*(p-lim))/p;
			std::swap(A,B),lim=std::max(A-B,0.0),lim=std::min(lim,p);
			f[i][j]+=(B*lim+0.5*lim*lim+A*(p-lim))/p;
			f[i][j]*=0.5;
		}
	}
	
	printf("%.12lf",f[1][1]);

	return 0;
}