#include <bits/stdc++.h>
using namespace std;
int main(){
    int N;
    cin >> N;
    vector<long int> a(N+1,0);
    a[0] = a[1] = 1;
    for(int i=2;i<=N;i++){
        a[i] = a[i-1] + a[i-2];
    }
    cout << a[N] << endl;
    return 0;
}