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

double P[5];
double dp[100][20];

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 += P[0] * solve(A + 1, rem - 1);   // 死ぬ
        res += (1 - P[0]) * solve(A + 1, rem); //生きる
        return res;
    }

    for(int mask=0;mask<1<<rem;mask++){
        double p = 1;

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

            if((mask >> i) & 1){
                // 生き残る
                p *= 1 - tmp;
            } else {
                p *= tmp;
            }
        }

        int acc = 0;
        for(int i=0;i<rem+1;i++){
            if((mask >> i) & 1){
                ++acc;
                continue;
            }

            res += p * solve(A + 1, acc);
            acc = 0;
        }
    }

    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;
}