package q2xx;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.InputMismatchException;

// O(KN^2)
public class Q281_3 {
	static InputStream is;
	static PrintWriter out;
	static String INPUT = "";
	
	static void solve()
	{
		int rem = 80-ni();
		double[] dead = new double[]{
				(double)ni()/100,
				(double)ni()/100,
				(double)ni()/100
		};
		
 		// 0.4*0.6*2*1
		// 0.6*0.6*1*2
		
		double[][] ep = new double[rem+1][15]; // [i][j]=残りi年で長さjになった状態からはじめたときの最終状態の期待値
		for(int i = 0;i < 15;i++)ep[0][i] = i;
		for(int t = 1;t <= rem;t++){
			ep[t][1] = ep[t-1][1] * (1.-dead[0]);
			double[] e = new double[14+1];
			double[] p = new double[14+1];
			e[0] = 0;
			p[0] = 1;
			for(int L = 2;L <= 14;L++){
				{
					double lp = L-1 > 1 ? dead[2] : dead[1];
					e[L-1] = p[L-1] = 0;
					for(int j = L-2;j >= 0;j--){
						e[L-1] += lp * (e[j] + ep[t-1][L-1-j-1] * p[j]);
						p[L-1] += lp * (p[j]);
						lp *= j == 1 ? 1.-dead[1] : 1.-dead[2];
					}
				}
				{
					double lp = dead[1];
					for(int j = L-1;j >= 0;j--){
						e[L] += lp * (e[j] + ep[t-1][L-j-1] * p[j]);
						p[L] += lp * (p[j]);
						lp *= j == 1 ? 1.-dead[1] : 1.-dead[2];
					}
				}
				double lp = 1;
				for(int j = L;j >= 0;j--){
					ep[t][L] += lp * (e[j] + ep[t-1][L-j] * p[j]);
					lp *= j == L || j == 1 ? 1.-dead[1]: 1.-dead[2];
				}
			}
		}
		out.printf("%.12f\n", ep[rem][14]*2);
	}
	
	public static void main(String[] args) throws Exception
	{
		long S = System.currentTimeMillis();
		is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes());
		out = new PrintWriter(System.out);
		
		solve();
		out.flush();
		long G = System.currentTimeMillis();
		tr(G-S+"ms");
	}
	
	private static boolean eof()
	{
		if(lenbuf == -1)return true;
		int lptr = ptrbuf;
		while(lptr < lenbuf)if(!isSpaceChar(inbuf[lptr++]))return false;
		
		try {
			is.mark(1000);
			while(true){
				int b = is.read();
				if(b == -1){
					is.reset();
					return true;
				}else if(!isSpaceChar(b)){
					is.reset();
					return false;
				}
			}
		} catch (IOException e) {
			return true;
		}
	}
	
	private static byte[] inbuf = new byte[1024];
	static int lenbuf = 0, ptrbuf = 0;
	
	private static int readByte()
	{
		if(lenbuf == -1)throw new InputMismatchException();
		if(ptrbuf >= lenbuf){
			ptrbuf = 0;
			try { lenbuf = is.read(inbuf); } catch (IOException e) { throw new InputMismatchException(); }
			if(lenbuf <= 0)return -1;
		}
		return inbuf[ptrbuf++];
	}
	
	private static boolean isSpaceChar(int c) { return !(c >= 33 && c <= 126); }
	private static int skip() { int b; while((b = readByte()) != -1 && isSpaceChar(b)); return b; }
	
	private static double nd() { return Double.parseDouble(ns()); }
	private static char nc() { return (char)skip(); }
	
	private static String ns()
	{
		int b = skip();
		StringBuilder sb = new StringBuilder();
		while(!(isSpaceChar(b))){ // when nextLine, (isSpaceChar(b) && b != ' ')
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}
	
	private static char[] ns(int n)
	{
		char[] buf = new char[n];
		int b = skip(), p = 0;
		while(p < n && !(isSpaceChar(b))){
			buf[p++] = (char)b;
			b = readByte();
		}
		return n == p ? buf : Arrays.copyOf(buf, p);
	}
	
	private static char[][] nm(int n, int m)
	{
		char[][] map = new char[n][];
		for(int i = 0;i < n;i++)map[i] = ns(m);
		return map;
	}
	
	private static int[] na(int n)
	{
		int[] a = new int[n];
		for(int i = 0;i < n;i++)a[i] = ni();
		return a;
	}
	
	private static int ni()
	{
		int num = 0, b;
		boolean minus = false;
		while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
		if(b == '-'){
			minus = true;
			b = readByte();
		}
		
		while(true){
			if(b >= '0' && b <= '9'){
				num = num * 10 + (b - '0');
			}else{
				return minus ? -num : num;
			}
			b = readByte();
		}
	}
	
	private static long nl()
	{
		long num = 0;
		int b;
		boolean minus = false;
		while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
		if(b == '-'){
			minus = true;
			b = readByte();
		}
		
		while(true){
			if(b >= '0' && b <= '9'){
				num = num * 10 + (b - '0');
			}else{
				return minus ? -num : num;
			}
			b = readByte();
		}
	}
	
	private static void tr(Object... o) { if(INPUT.length() != 0)System.out.println(Arrays.deepToString(o)); }
}