#include <fstream>
using namespace std;
const int mod=982451653;
ifstream in("kfib.in");
ofstream out("kfib..out");
int fibb(int n,int a,int b) {
    if(n==0)
        return a;
    return fibb(n-1,b,a+b);
}
int main() {
    int n;
    in>>n;
    out <<fibb(n,0,1);
    return 0;
}