题解 | 无限长正整数排列字符串

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        
        StringBuilder sb = new StringBuilder();
        for (int i = 1; sb.length() < n; i++) {
            sb.append(i);
        }
        
        System.out.println(sb.charAt(n - 1));
    }
}