#include <iostream>
#include <vector>
using namespace std;

int main(){
    int n;
    cin >> n;
    vector<long long int> ans(n+1);
    ans[0] = ans[1] = 1;
    for(int i = 2; i <= n; i++) ans[i] = ans[i-1]+ans[i-2];
    cout << ans[n] << endl;
    return 0;
}