#include<cstdio>
#include<vector>
#include<algorithm>
#include<iostream>
using namespace std;
int main(){
    double dp[21][32];
    int n;
    double p0,p1,p2;
    cin>>n>>p0>>p1>>p2;
    p0=(100-p0)/100;p1=(100-p1)/100;p2=(100-p2)/100;
    for(int j=0;j<32;j++){
        if(j%16==0||j%16==15)dp[n-60][j]=0;
        else dp[n-60][j]=1.0;
    }
    for(int i=n-60+1;i<=20;i++){
        for(int j=0;j<32;j++){
            if(j%16==0||j%16==15)dp[i][j]=0;
            else{
                dp[i][j]=dp[i-1][j]*dp[i-1][j-1]*dp[i-1][j+1]*p2;
                dp[i][j]+=dp[i-1][j]*dp[i-1][j-1]*(1-dp[i-1][j+1])*p1;
                dp[i][j]+=dp[i-1][j]*(1-dp[i-1][j-1])*dp[i-1][j+1]*p1;
                dp[i][j]+=dp[i-1][j]*(1-dp[i-1][j-1])*(1-dp[i-1][j+1])*p0;
            }
        }
    }
    double sum=0;
    for(int i=0;i<32;i++)sum+=dp[20][i];
    cout<<fixed<<sum<<endl;
}