def get_pell(n):
	 
	if (n <= 2): 
		return n 
	a = 1
	b = 2
	for i in range(3, n+1): 
		c = 2 * b + a 
		a = b 
		b = c 
	return b 
def get_pell(n):
    if n <= 2:
        return n
    a = 1
    b = 2
   
    i = 3
    while i < n + 1:
        c = 2 * b + a
        a = b
        b = c
        i += 1
    return b