#include <bits/stdc++.h>
using namespace std; 
int x;
int a[35];
int main(){
	while(cin >> x){
		a[1] = 1;
		a[2] = 2;
		for(int i=3;i<=x;i++){
			a[i]=a[i-1]+a[i-2];
		} 
		cout << a[x] << endl;
	}
	return 0;
}