N = int(input()) K = int(input()) taro_num = [0]*(6*N+1) jiro_num = [0]*(6*N+1) taro_num[0] = 1 jiro_num[0] = 1 for i in range(1,N+1): new_taro_num = [0]*(6*N+1) for j in range(6*N+1): if i <= K: for s in range(4,7): if j-s >= 0: new_taro_num[j] += taro_num[j-s] / 3 else: for s in range(1,7): if j-s >= 0: new_taro_num[j] += taro_num[j-s] / 6 taro_num = new_taro_num new_jiro_num = [0]*(6*N+1) for j in range(6*N+1): for s in range(1,7): if j-s >= 0: new_jiro_num[j] += jiro_num[j-s] / 6 jiro_num = new_jiro_num result = 0 for i in range(0,6*N): for j in range(i+1, 6*N+1): result += jiro_num[i] * taro_num[j] print(result)