#include<bits/stdc++.h>
using namespace std;
int main() {
    int n, dp[10001] = {};
    cin >> n;
    {dp[1] = 1; dp[2] = 1; }
    for (int i = 3; i <= n; i++) dp[i] = dp[i - 1] + dp[i - 2];
    cout << dp[n];
}