题解 | #自守数#

import java.util.*;
public class Main{
    public static void main(String[] args){
        Scanner scan = new Scanner(System.in);
        while(scan.hasNext()){
            int n = scan.nextInt();
            int[] count = new int[n+1];
            int sum = 0;
            for(int i = 0; i<=n; i++){
                String s = Integer.toString(i);
                if((i*i - i) % (Math.pow(10,s.length())) == 0){
                    count[i]++;
                }
                else{
                    continue;
                }
            }
            for(int i : count){
                if(i>0){
                    sum++;
                }
//                 System.out.print(i);
            }
            System.out.print(sum);
            
        }
        scan.close();
        
    }
}