n = int(input("Give N: "))
print("N is " + str(n))

if n < 1:
	print("N must be positive")
else:
	print("OK, N is positive")

	result = 1
	for i in range(1, n+1):
		#result = result * i
		result *= i
		
	print(str(n) + "! = " + str(result))