def cal_sum(n):
	 
	a = 3
	b = 0
	c = 2
	if (n == 0): 
		return 3
	if (n == 1): 
		return 3
	if (n == 2): 
		return 5
	sum = 5
	while (n > 2): 
		d = a + b 
		sum = sum + d 
		a = b 
		b = c 
		c = d 
		n = n-1
	return sum
def cal_sum(n):
    a = 3
    b = 0
    c = 2
    if 0 == n:
        return 3
    if n == 1:
        return 3
    if n == 2:
       
        return 5
    sum = 5
    while n > 2:
        d = a + b
        sum = sum + d
        a = b
        b = c
        c = d
        n = n - 1
    return sum