It is November 18 now in Japan. By the way, 11 and 18 are adjacent Lucas numbers.  You are given an integer N. Find the N-th Lucas number.  Here, the i-th Lucas number L_i is defined as follows:    * L_0=2   * L_1=1   * L_i=L_{i-1}+L_{i-2} (i≥2)
def Lucas(n):
  if n==0: return 2
  if n==1: return 1
  a=2
  b=1
  for i in range(2,n):
    a,b=b,a+b
  return b
N=int(input())
print(Lucas(N))

def Lucas(n):
  if n==0: return 2
  if n==1: return 1
  a=2
  b=1
  for i in range(2,n+1):
    a,b=b,a+b
  return b
N=int(input())
print(Lucas(N))