3n+1.py

def n31(a):# a = initial number
    c = 0
    l = [a]
    while a != 1:
        if a % 2 == 0:#if even divide it by 2
            a = a // 2
        elif a % 2 == 1:#if odd 3n+1
            a = 3*a +1
        c += 1#counter
        l += [a]
    return l , c
    
def main():
    
    print(n31(43))
    print(n31(98)[0][-1])# = a
    print("It took {0} steps.".format(n31(13)[1]))#optional finish

if __name__ == '__main__':
    main()