题解 | #自守数#

public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        if(sc.hasNext()){
            int input = sc.nextInt();
            int n=0;
            for(int i=0;i<=input;i++){
                if(i==(i*i)%10){
                    n++;
                }
            }
            System.out.print(n);
        }
    }
}