def reverse_factorial(num):
    try:
        float(num)
    except:
	    return None
    i = 2
    if num == abs(num):
        j = 1
    else:
        j = -1
        num = abs(num)
    while num > 1:
        num /= i
        i += 1
    return j*i-1 if num == 1 else None

for num in [3628800,479001600,6,18,"a",1.2,-24]:
    rev_fac = reverse_factorial(num)
    print(num," NONE") if rev_fac is None else print(num," = ",rev_fac,"!",sep="")