#!/usr/bin/env python

try:
	import psyco
	psyco.full()
except:
	pass

def isprime(num):
	test = 3 
	# Since no even number exists in the passed number.
	condition = num/2 
	# We store the num/2 in a variable to avoid repeated calculations of it in the loop.
	while test<condition: 
	# A number can at max be divided by some value the half of it,
	# For instance, 15 can be at max divided by 3, and 5 but nothing above 7, which is 15/2 (Integer Division).
		x = num % test
		if x==0:
			return 0
		test+=2 
		# No need to check if number is divisible by an even number so we skip to odds.
	return 1
	# Happens if the loop is complete with no return.
		

if __name__ == '__main__':
	# Get the input
	ip = int(raw_input("Enter the number to check: "))
	
	# Check if input is even and accordingly call the function.
	if ip == 2:
		print ip, "is a prime."
	elif ip&1 and isprime(ip):
		print ip, "is a prime."
	else:
		print ip, "is not a prime."
		
	# Obfuscated? Figure this one yourself o_O