def bell_number(n):   
    bell = [[0 for i in range(n+1)] for j in range(n+1)] 
    bell[0][0] = 1
    for i in range(1, n+1): 
        bell[i][0] = bell[i-1][i-1]  
        for j in range(1, i+1): 
            bell[i][j] = bell[i-1][j-1] + bell[i][j-1]   
    return bell[n][0] 