#include<iostream>
#include<algorithm>
#include<cstring>
#include<cstdio>
using namespace std;
double dp[1050][1050];
int n,m;double p;
double eps=1e-9;
double mix(double t0,double t1){
    if(t0>t1)swap(t0,t1);
    double ret=0;
    ret+=t0/2;
    double dlt=t1-t0;
    if(dlt>=p)ret+=(p+t0)/2;
    else{
        ret+=(t0+dlt/2)*(dlt)/(2*p)+(t1)*(p-dlt)/(2*p);
    }
    return ret;
}
int main(){
    cin>>n>>m>>p;
    for(int i=2;i<=n;i++){
        dp[i][1]=p/4.0*(i-1);
    }
    for(int i=2;i<=m;i++){
        dp[1][i]=p/4.0*(i-1);
    }
    for(int i=2;i<=n;i++){
        for(int j=2;j<=m;j++){
            dp[i][j]=mix(dp[i-1][j],dp[i][j-1]);
        }
    }
    printf("%.8lf\n",dp[n][m]);
}