#include <bits/stdc++.h>
using namespace std;

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

    long long f[100005];

    f[1] = 1;
    f[2] = 1;

    for (int i = 3; i <= n; i++)
        f[i] = f[i - 1] + f[i - 2];

    cout << f[n];

    return 0;
}