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;
		sc.close();

		int n = 80 - a;
		double[][] dp = new double[n + 1][15];
		for (int i = 0; i < 15; i++) {
			dp[0][i] = i;
		}

		for (int year = 1; year <= n; year++) {
			for (int tooth = 1; tooth < 15; tooth++) {
				for (int bit = 0; bit < 1 << tooth; bit++) {

					/*
					 * 1<<toothからbitに遷移する確率pを計算する
					 */
					double p = 1;
					for (int t = 0; t < tooth; t++) {
						boolean injured = ((bit >> t & 1) == 1);// 歯tが抜けていればtrue
						int count = (t == 0 ? 0 : 1) + (t == tooth - 1 ? 0 : 1);
						if (count == 0) {
							// 両隣が抜歯済み
							p *= injured ? p0 : 1 - p0;
						} else if (count == 1) {
							// 片側が抜歯済み
							p *= injured ? p1 : 1 - p1;
						} else {
							// 両隣が生えてる
							p *= injured ? p2 : 1 - p2;
						}
					}

					double sum = 0;
					int seq = 0;
					for (int l = 0; l <= tooth; l++) {
						if ((bit >> l & 1) == 0 && (l < tooth)) {
							seq++;
						} else {
							sum += dp[year - 1][seq];
							seq = 0;
						}
					}
					dp[year][tooth] += p * sum;
				}
			}
		}
		// System.out.println(Arrays.deepToString(dp));
		System.out.println(dp[n][14] * 2);
	}

}