题解 | #数字构造#

import java.util.Scanner;

public class Main {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);

        while(in.hasNext()){
            // solution1(in);
            solution2(in);
        }
    }

    /**
     * 模拟法: 找规律
     * 简化
     * @param in
     */
    private static void solution1(Scanner in){
        int s = in.nextInt();

        int multi = s/3;
        int mod = s%3;
        StringBuilder sb = new StringBuilder();
        if(mod == 1){
            sb.append(1);
        }
        for(int i=1; i<=multi; i++){
            sb.append("21");
        }
        if(mod == 2){
            sb.append(2);
        }

        System.out.println(sb);
    }

    /**
     * 模拟法: 找规律
     * @param in
     */
    private static void solution2(Scanner in){
        int s = in.nextInt();

        int multi = s/3;
        int mod = s%3;
        StringBuilder sb = new StringBuilder();
        if(mod == 0){
            for(int i=1; i<=multi; i++){
                sb.append("21");
            }
        }else if(mod == 1){
            for(int i=1; i<=multi; i++){
                sb.append("12");
            }
            sb.append(1);
        }else if(mod == 2){
            for(int i=1; i<=multi; i++){
                sb.append("21");
            }
            sb.append(2);
        }

        System.out.println(sb);
    }
}