将一个正整数分解质因数。例如：输入90,打印出90=2*3*3*

shu =int(input("一个正整数:"))

s=[]

for i in range(2,int((shu+2)/2)):

    a =True

    while a ==True:

        if shu % i ==0:

            s.append(str(i))

            shu = shu/i

        else:

            a=False

print("*".join(s))