#include <iostream>
using namespace std;

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

    long long dp[1001] = {0,};

    dp[0] = 1;
    dp[1] = 1;

    for (int i = 2; i <= n; i++) {
        dp[i] = dp[i - 1] + dp[i - 2];
    }

    cout << dp[n];

    return 0;
}