import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    int K = sc.nextInt();
    // dp1[i][j]は普通のさいころをi+1個投げて和がjとなる確率
    double[][] dp1 = new double[N][6 * N + 1];
    // dp2[i][j]はイカサマさいころをmin(K, i+1)個、普通のさいころをi+1-min(K, i+1)個投げて和がjとなる確率
    double[][] dp2 = new double[N][6 * N + 1];
    for(int j = 1; j <= 6; j++) {
      dp1[0][j] = (double)1 / (double)6; 
    }
    for(int i = 1; i < N; i++) {
      for(int j = 0; j < 6 * N + 1; j++) {
        for(int k = 1; k <= 6; k++) {
          if(j - k > 0) dp1[i][j] += (double)1 / (double)6 * dp1[i - 1][j - k];
        }
      }
    }
    if(K > 0) {
      for(int j = 4; j <= 6; j++) {
        dp2[0][j] = (double)1 / (double)3;
      }
    } else {
      for(int j = 1; j <= 6; j++) {
        dp2[0][j] = (double)1 / (double)6; 
      }
    }
    for(int i = 1; i < N; i++) {
      for(int j = 0; j < 6 * N + 1; j++) {
        if(i < K) {
          for(int k = 4; k <= 6; k++) {
            if(j - k > 0) dp2[i][j] += (double)1 / (double)3 * dp2[i - 1][j - k];
          }
        } else {
          for(int k = 1; k <= 6; k++) {
            if(j - k > 0) dp2[i][j] += (double)1 / (double)6 * dp2[i - 1][j - k];
          }
        }
      }
    }
    double ans = 0;
    for(int j1 = 1; j1 < 6 * N + 1; j1++) {
      for(int j2 = 1; j2 < j1; j2++) {
        ans += dp1[N - 1][j2] * dp2[N - 1][j1];
      }
    }
    System.out.println(ans);
  }
}