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; public class Q281_2 { 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]); for(int L = 2;L <= 14;L++){ double[] e = new double[L+1]; double[] p = new double[L+1]; e[0] = 0; p[0] = 1; for(int i = 1;i <= L;i++){ double lp = i < L && i > 1 ? dead[2] : dead[1]; for(int j = i-1;j >= 0;j--){ e[i] += lp * (e[j] + ep[t-1][i-j-1] * p[j]); p[i] += 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)); } }