def InvFactorial(num):
    out = CalcInvFactorial(num)
    return('Inverse factorial of %s is %s' % (num, out) )
        

def CalcInvFactorial(n):
    i = 0
    invFac = 0
    while (invFac != 1):
        i += 1
        invFac = n / i
        if (n % i != 0):
            return 'NONE'
        else:
            n = invFac
    return i

	
print(InvFactorial(3628800))
print(InvFactorial(479001600))
print(InvFactorial(6))
print(InvFactorial(18))