import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import java.util.PriorityQueue;
import java.util.Queue;
public class Main {
	public static double[][] dp;
	public static double p0;
	public static double p1;
	public static double p2;
	public static void main(String[] args) throws NumberFormatException, IOException{
		ContestScanner in = new ContestScanner();
		int a = in.nextInt();
		p0 = in.nextInt();
//		p0 = 100 - p0;
		p0 *= 0.01;
		p1 = in.nextInt();
//		p1 = 100 - p1;
		p1 *= 0.01;
		p2 = in.nextInt();
//		p2 = 100 - p2;
		p2 *= 0.01;
		dp = new double[21][15];
		for(int i=0; i<=20; i++){
			for(int j=0; j<=14; j++){
				dp[i][j] = -1;
			}
		}
//		dp[1][1] = 1-p0;
		System.out.println(dfs(80-a, 14)*2);
	}
	
	public static double dfs(int year, int ha){
		if(year == 0) return ha;
		if(ha == 1) return dp[year][ha] = (1-p0)*dfs(year-1, 1);
		if(dp[year][ha] >= 0) return dp[year][ha];
		dp[year][ha] = 0;
		for(int i=0; i<1<<ha; i++){
			int bit = 0;
			int left = 0;
			double p = 1;
			double prob = 0;
			while(bit<ha){
				if((i&(1<<bit)) > 0){
					left++;
					p *= bit==0||(1<<ha-1)==(1<<bit)?1-p1:1-p2;
				}else{
					if(left > 0){
						prob += dfs(year-1, left);
					}
					p *= bit==0||(1<<ha-1)==(1<<bit)?p1:p2;
					left = 0;
				}
				bit++;
			}
			if(left > 0){
				prob += dfs(year-1, left);
			}
			dp[year][ha] += p*prob;
			left = 0;
		}
		return dp[year][ha];
	}
}


class MyComp implements Comparator<int[]>{
	public int compare(int[] a, int[] b) {
		return a[0] - b[0];
	}
}

class Reverse implements Comparator<Integer>{
	public int compare(Integer arg0, Integer arg1) {
		return arg1 - arg0;
	}
}

class Node{
	int id;
	List<Node> edge = new ArrayList<Node>();
	public Node(int id){
		this.id = id;
	}
	public void createEdge(Node node){
		edge.add(node);
	}
}

class ContestWriter{
	private PrintWriter out;
	public ContestWriter(String filename) throws IOException{
		out = new PrintWriter(new BufferedWriter(new FileWriter(filename)));
	}
	
	public ContestWriter() throws IOException{
		out = new PrintWriter(System.out);
	}
	
	public void println(String str){
		out.println(str);
	}
	
	public void print(String str){
		out.print(str);
	}
	
	public void close(){
		out.close();
	}
}

class ContestScanner{
	private BufferedReader reader;
	private String[] line;
	private int idx;
	public ContestScanner() throws FileNotFoundException{
		reader = new BufferedReader(new InputStreamReader(System.in));
	}

	public ContestScanner(String filename) throws FileNotFoundException{
		reader = new BufferedReader(new InputStreamReader(new FileInputStream(filename)));
	}
	
	public String nextToken() throws IOException{
		if(line == null || line.length <= idx){
			line = reader.readLine().trim().split(" ");
			idx = 0;
		}
		return line[idx++];
	}
	public long nextLong() throws IOException, NumberFormatException{
		return Long.parseLong(nextToken());
	}
	public int nextInt() throws NumberFormatException, IOException{
		return (int)nextLong();
	}
	public double nextDouble() throws NumberFormatException, IOException{
		return Double.parseDouble(nextToken());
	}
}