答案answer

# include<stdio.h>

# include<iostream>

using namespace std; 

int main(){

int a; 

cin >> a; 

int dp[999]; 

dp[1] = 1; 

dp[2] = 2; 

for (int i = 3; i <= a; i++) { 

dp[i] = dp[i - 1] + dp[i - 2]; 

} 

cout<<dp[a] << endl;

 return 0; 

}