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

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