普及/提高????????入门吧

#include<bits/stdc++.h>
using namespace std;
int a[50] = {1,1};
int n;
int main(){
cin >> n;
if(n == 1 || n == 2){
cout << "1";
}else{
for(int i = 2;i < n;i++){
a[i] = a[i-2] + a[i-1];
}
cout << a[n-1];
}
return 0;
}