#include <iostream>
using namespace std;
int main()
{
    int n;
    while (cin>>n) {
        long long a[51]={};
        a[0]=a[1]=1;
        for(int i=2;i<=n;++i) a[i]=a[i-1]+a[i-2];
        cout<<a[n]<<endl;
    }
}