package no162;

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int a = sc.nextInt();
		double p0 = sc.nextInt() / 100.0;
		double p1 = sc.nextInt() / 100.0;
		double p2 = sc.nextInt() / 100.0;
		double[][] dp = new double[21][15];
		for(int i=0;i<15;i++) {
			dp[0][i] = i;
		}
		int n = 80 - a;
		for(int i=1;i<=n;i++) {
			for(int j=1;j<15;j++) {
				double e = 0;
				for(int k=0;k<1<<j;k++) { //抜け方
					double p = 1;
					for(int l=0;l<j;l++) {
						boolean nuketa = ((k>>l&1) == 1);
						int count = (l == 0 ? 0 : 1) + (l == j - 1 ? 0 : 1);
						if (count == 0) {
							p *= nuketa ? p0 : 1 - p0;
						}else if(count == 1) {
							p *= nuketa ? p1 : 1 - p1;
						}else{
							p *= nuketa ? p2 : 1 - p2;
						}
					}
					double sum = 0;
					int seq = 0;
					for(int l=0;l<=j;l++) {
						if ((k>>l&1) == 0 && (l < j)) {
							seq++;
						}else{
							sum += dp[i-1][seq];
							seq = 0;
						}
					}
					e += p * sum;
				}
				dp[i][j] = e;
			}
		}
//		System.out.println(Arrays.deepToString(dp));
		System.out.println(dp[n][14] * 2);
	}

}