爬樓梯

#include <iostream>
#include <vector>
#include <algorithm>
#include <cstdio>
#include <map>
typedef long long LL;
const int N = 100;
LL f[N];
using namespace std;
int main(){
	int n;
	
	f[1] = 1;
	f[2] = 2;
	for(int i =3; i <100; i++){
		f[i] = f[i-1] + f[i-2];
	}
	cin>>n;
	cout<<f[n]<<endl;
	return 0;
}