题解 | #杨辉三角的变形#

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Scanner;

/**
 * @author eagle2020
 * @date 2021/9/29
 */
public class Main {

    public static void main(String[] args) throws IOException {
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNext()) {
            int n = scanner.nextInt();
            int len = n * 2 - 1;
            int[] dp = new int[n * 2 - 1];
            dp[0] = 1;
//             for(int i = 0; i < n* 2 - 1; i++){
//                  System.out.print(dp[i] + "\t");
//             }
            //一行一行的推到
            for (int i = 2; i <= n; i++) {
                for(int j = len - 1; j >= 0; j--){
                    dp[j] = (j - 2 >= 0 ? dp[j - 2] : 0) + (j - 1 >= 0 ? dp[j - 1] : 0) + dp[j];
                }
            }
//             for(int i = 0; i < n* 2 - 1; i++){
//                  System.out.print(dp[i] + "\t");
//             }
            int index = -1;
            for(int i = 0; i < n * 2 - 1; i++){
                if(dp[i] % 2 == 0){
                    index = i + 1;
                    break;
                }
            }
            System.out.println(index);
        }

    }
}