#include <iostream>

using namespace std;


int count;

int jump(int n){
    if(n == 0)  return 1;
    if(n < 0) return 0;
    int l = jump(n - 1);
    int r = jump(n - 2);
    return l + r;
}


int main(){
    int n = 0;
    cin >> n;

    cout << jump(n) << endl;

    return 0;
}