题解 | #跳台阶#

import sys

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

n = int(input())
dp =[0 for i in range(n+1)]

dp[0]=1
dp[1]=1
if  n ==1 or n==1:
    print(1) 
else:
    for i in range(2,n+1):
        dp[i] = dp[i-1] +dp[i-2]    
    print(dp[n])