#include <fstream>

using namespace std;
unsigned long long int v[1000];
int main()
{
    ifstream cin("nunta.in");
    ofstream cout("nunta.out");
    v[1]=1;
    v[2]=1;
    int cnt=2;
    while(cnt<=1000)
    {
        v[cnt+1]=v[cnt]+v[cnt-1];
        cnt++;
    }
    int n;
    cin>>n;
    cout<<v[n+1];
    return 0;
}