import java.util.Scanner;
// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int n = in.nextInt();
int[] dp = new int[n];
dp[0] = 1;
dp[1] = 1;
for(int i = 2; i < n; i++){
dp[i] = dp[i - 2] + dp[i - 1];
}
System.out.println(dp[n-1]);
}
}



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