# check if a given number is prime or not

def isPrime(n) :  
	if (n <= 1) : 
		return False
	if (n <= 3) : 
		return True
	if (n % 2 == 0 or n % 3 == 0) : 
		return False

	i = 5
	while(i * i <= n) : 
		if (n % i == 0 or n % (i + 2) == 0) : 
			return False
		i = i + 6
	return True