上台阶

#include <iostream>
using namespace std;
int n;
int shangtaijie(int n){
if(n==0)return 1;
if(n<0)return 0;
return shangtaijie(n-1)+shangtaijie(n-2);

}

int main(){
    cin>>n;
    cout<<shangtaijie(n);
}