题解 | 数楼梯

#两种方法
import sys

n=int(input())
result=[0]*(n+1)
for i in range(1,n+1):
    if i==1:
        result[i]=1
    elif i==2:
        result[i]=2
    else:
        result[i]=(result[i-1]+result[i-2])%998244353
print(result[n])



'''
MOD = 998244353
n = int(input())
if n == 1:
    print(1)
elif n == 2:
    print(2)
else:
    a, b = 1, 2  
    for _ in range(3, n + 1):
        c = (a + b) % MOD
        a = b
        b = c
    print(b)
'''