题解 | #兔子的数量#

import sys

def rabbit_num(n):
    if n == 0:
        return 0
    elif n == 1:
        return 2
    elif n == 2:
        return 3
    else:
        return rabbit_num(n-1) + rabbit_num(n-2)

month = int(input())
print(rabbit_num(month))
    

for line in sys.stdin:
    a = line.split()
    print(int(a[0]) + int(a[1]))