#include <bits/stdc++.h>
using namespace std;

double dp[100][100];
double P[10];

double solve(int A, int rem){
    if(A >= 80)return rem;
    if(rem == 0)return 0;

    double &res = dp[A][rem];
    if(res >= -0.5)return res;

    res = 0;

    if(rem == 1){
        res += (1 - P[0]) * solve(A + 1, 1);
        return res;
    }

    for(int s=0;s<rem;s++){
        double p = 1;
        if(s == 0 || s == rem - 1){
            p *= 1 - P[1];
        } else {
            p *= 1 - P[2];
        }

        if(s - 1 == 0){
            p *= P[1];
        }
        if(s - 1 > 0){
            p *= P[2];
        }

        if(s + 1 == rem - 1){
            p *= P[1];
        }
        if(s + 1 < rem - 1){
            p *= P[2];
        }

        res += p * solve(A + 1, 1);
    }

    for(int len=2;len<=rem;len++){
        for(int s=0;s+len<=rem;s++){
            int t = s + len - 1;

            double p = 1;

            if(s - 1 < 0){
                p *= 1 - P[1];
            }
            if(s - 1 == 0){
                p *= P[1] * (1 - P[2]);
            }
            if(s - 1 > 0){
                p *= P[2] * (1 - P[2]);
            }

            if(t + 1 > rem - 1){
                p *= 1 - P[1];
            }
            if(t + 1 == rem - 1){
                p *= (1 - P[2]) * P[1];
            }
            if(t + 1 < rem - 1){
                p *= (1 - P[2]) * P[2];
            }

            for(int k=0;k<len-2;k++)p *= 1 - P[2];

            res += p * solve(A + 1, len);
        }
    }

    return res;
}

int main(){
    memset(dp, -1, sizeof(dp));

    int A;
    cin >> A;

    cin >> P[0] >> P[1] >> P[2];
    P[0] /= 100;
    P[1] /= 100;
    P[2] /= 100;

    printf("%.10f\n", 2 * solve(A, 14));
    return 0;
}