import java.util.*;
 
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
 
        if (n <= 1) {
            System.out.println(1);
            return;
        }
 
        int[] dp = new int[n + 1];
        dp[0] = 1;
        dp[1] = 1;
 
        for (int i = 2; i <= n; i++) {
            dp[i] = dp[i - 1] + dp[i - 2];
        }
 
        System.out.println(dp[n]);
    }
}

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NA==

4