import java.io.IOException;
import java.util.Arrays;
import java.util.InputMismatchException;

public class Main {
	double[][] taro, jiro;
	int t;

	double taro(int k, int s) {
		if (s <= 0) {
			return 0;
		}
		if (0 <= taro[k][s]) {
			return taro[k][s];
		}
		if (k == 1) {
			if (1 <= t && 4 <= s && s <= 6) {
				return 1. / 3.;
			}
			if (t == 0 && 1 <= s && s <= 6) {
				return 1. / 6.;
			}
			return 0;
		}

		double res = 0;
		if (k <= t) {
			res += taro(k - 1, s - 4) / 3.;
			res += taro(k - 1, s - 5) / 3.;
			res += taro(k - 1, s - 6) / 3.;
		} else {
			res += taro(k - 1, s - 1) / 6.;
			res += taro(k - 1, s - 2) / 6.;
			res += taro(k - 1, s - 3) / 6.;
			res += taro(k - 1, s - 4) / 6.;
			res += taro(k - 1, s - 5) / 6.;
			res += taro(k - 1, s - 6) / 6.;
		}
		return taro[k][s] = res;
	}

	double jiro(int k, int s) {
		if (s <= 0) {
			return 0;
		}
		if (0 <= jiro[k][s]) {
			return jiro[k][s];
		}
		if (k == 1) {
			if (1 <= s && s <= 6) {
				return 1. / 6.;
			}
			return 0;
		}

		double res = 0;
		res += jiro(k - 1, s - 1) / 6.;
		res += jiro(k - 1, s - 2) / 6.;
		res += jiro(k - 1, s - 3) / 6.;
		res += jiro(k - 1, s - 4) / 6.;
		res += jiro(k - 1, s - 5) / 6.;
		res += jiro(k - 1, s - 6) / 6.;
		return jiro[k][s] = res;
	}

	void run() {
		MyScanner sc = new MyScanner();

		int n = sc.nextInt();
		t = sc.nextInt();

		taro = new double[n + 1][6 * n + 1];
		jiro = new double[n + 1][6 * n + 1];
		for (int i = 0; i < n + 1; i++) {
			Arrays.fill(taro[i], -1);
			Arrays.fill(jiro[i], -1);
		}

		double ans = 0;
		for (int i = n; i <= 6 * n; i++) {
			for (int j = i + 1; j <= 6 * n; j++) {
				double k1 = taro(n, j);
				double k2 = jiro(n, i);
				ans += k1 * k2;
			}
		}
		System.out.println(ans);
	}

	public static void main(String[] args) {
		new Main().run();
	}

	public void mapDebug(int[][] a) {
		System.out.println("--------map display---------");
		for (int i = 0; i < a.length; i++) {
			for (int j = 0; j < a[i].length; j++) {
				System.out.printf("%3d ", a[i][j]);
			}
			System.out.println();
		}
		System.out.println("----------------------------" + '\n');
	}

	class MyScanner {
		int read() {
			try {
				return System.in.read();
			} catch (IOException e) {
				throw new InputMismatchException();
			}
		}

		boolean isSpaceChar(int c) {
			return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
		}

		boolean isEndline(int c) {
			return c == '\n' || c == '\r' || c == -1;
		}

		int nextInt() {
			return Integer.parseInt(next());
		}

		int[] nextIntArray(int n) {
			int[] array = new int[n];
			for (int i = 0; i < n; i++)
				array[i] = nextInt();
			return array;
		}

		long nextLong() {
			return Long.parseLong(next());
		}

		long[] nextLongArray(int n) {
			long[] array = new long[n];
			for (int i = 0; i < n; i++)
				array[i] = nextLong();
			return array;
		}

		double nextDouble() {
			return Double.parseDouble(next());
		}

		double[] nextDoubleArray(int n) {
			double[] array = new double[n];
			for (int i = 0; i < n; i++)
				array[i] = nextDouble();
			return array;
		}

		String next() {
			int c = read();
			while (isSpaceChar(c))
				c = read();
			StringBuilder res = new StringBuilder();
			do {
				res.appendCodePoint(c);
				c = read();
			} while (!isSpaceChar(c));
			return res.toString();
		}

		String[] nextStringArray(int n) {
			String[] array = new String[n];
			for (int i = 0; i < n; i++)
				array[i] = next();

			return array;
		}

		String nextLine() {
			int c = read();
			while (isEndline(c))
				c = read();
			StringBuilder res = new StringBuilder();
			do {
				res.appendCodePoint(c);
				c = read();
			} while (!isEndline(c));
			return res.toString();
		}
	}
}