#include<iostream>
#include<cstring>
#include<algorithm>
using namespace std;
const int N=30;
int a[N];
int main(){
    int n;
    a[0]=1,a[1]=1,a[2]=2;
    while(cin>>n){
        for(int i=3;i<=n;i++) a[i]=a[i-1]+a[i-2];
        cout<<a[n]<<endl;
    }
    return 0;
}