求丑数

def uglyNum(N: int):
    if N < 1:
        return 0
    elif N == 1:
        return 1
    else:
        baseNum = [2, 3, 5]
        uglyNumList = [1]
        i = 1
        num = 2
        while True:
            flag = num
            for x in baseNum:
                while True:
                    if flag % x > 0:
                        break
                    else:
                        flag = flag // x
            if(flag == 1):
                uglyNumList.append(num)
                i += 1
            if i == N:
                return uglyNumList
            num += 1


print(uglyNum(20))