import java.io.*; import java.util.*; import java.util.stream.*; public class Main { public static void main(String[] args) throws Exception { Scanner sc = new Scanner(); int p = sc.nextInt(); int c = sc.nextInt(); int[] primes = new int[]{2, 3, 5, 7, 11, 13}; int[] notprimes = new int[]{4, 6, 8, 9, 10, 12}; ArrayDeque deq = new ArrayDeque<>(); deq.add(1.0); for (int i = 0; i < p; i++) { ArrayDeque next = new ArrayDeque<>(); while (deq.size() > 0) { double x = deq.poll(); for (int y : primes) { next.add(x * y); } } deq = next; } for (int i = 0; i < c; i++) { ArrayDeque next = new ArrayDeque<>(); while (deq.size() > 0) { double x = deq.poll(); for (int y : notprimes) { next.add(x * y); } } deq = next; } double sum = 0; while (deq.size() > 0) { sum += deq.poll(); } System.out.println(new java.math.BigDecimal(sum / Math.pow(6, p + c)).toPlainString()); } } class Utilities { static String arrayToLineString(Object[] arr) { return Arrays.stream(arr).map(x -> x.toString()).collect(Collectors.joining("\n")); } static String arrayToLineString(int[] arr) { return String.join("\n", Arrays.stream(arr).mapToObj(String::valueOf).toArray(String[]::new)); } } class Scanner { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); StringTokenizer st = new StringTokenizer(""); StringBuilder sb = new StringBuilder(); public Scanner() throws Exception { } public int nextInt() throws Exception { return Integer.parseInt(next()); } public long nextLong() throws Exception { return Long.parseLong(next()); } public double nextDouble() throws Exception { return Double.parseDouble(next()); } public int[] nextIntArray() throws Exception { return Stream.of(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray(); } public String next() throws Exception { while (!st.hasMoreTokens()) { st = new StringTokenizer(br.readLine()); } return st.nextToken(); } }