[2193] 이친수

n = int(input())
dp = [0, 1, 1]
for i in range(3, 91):
    dp.append(dp[i-2]+dp[i-1])
print(dp[n])

 

n	1	2	3	4	5
f(n)	1	1	2	3	5
-	1	10	100, 101	1000, 1010, 1001	10000, 10101, 10100. 10010, 10001

dp[n] = dp[n-1]+dp[n-2]