题解 | #数字构造#

#include <iostream>
#include <string>
using namespace std;

int main() {
    int s;
    cin >> s;
    
    string result;
    if (s % 3 == 0) {
        int pairs = s / 3;
        for (int i = 0; i < pairs; i++) {
            result += "21";
        }
    } else if (s % 3 == 1) {
        int pairs = (s - 1) / 3;
        for (int i = 0; i < pairs; i++) {
            result += "12";
        }
        result += "1";
    } else {  // s % 3 == 2
        int pairs = (s - 2) / 3;
        for (int i = 0; i < pairs; i++) {
            result += "21";
        }
        result += "2";
    }
    
    cout << result << endl;
    return 0;
}

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int s = sc.nextInt();
        
        StringBuilder result = new StringBuilder();
        if (s % 3 == 0) {
            int pairs = s / 3;
            for (int i = 0; i < pairs; i++) {
                result.append("21");
            }
        } else if (s % 3 == 1) {
            int pairs = (s - 1) / 3;
            for (int i = 0; i < pairs; i++) {
                result.append("12");
            }
            result.append("1");
        } else {  // s % 3 == 2
            int pairs = (s - 2) / 3;
            for (int i = 0; i < pairs; i++) {
                result.append("21");
            }
            result.append("2");
        }
        
        System.out.println(result);
    }
}

s = int(input())

result = ""
if s % 3 == 0:
    pairs = s // 3
    result = "21" * pairs
elif s % 3 == 1:
    pairs = (s - 1) // 3
    result = "12" * pairs + "1"
else:  # s % 3 == 2
    pairs = (s - 2) // 3
    result = "21" * pairs + "2"

print(result)