3. 

import java.util.Scanner;

class Main {

  public static void main(String[] args) {

    int m;

    int n;

Scanner scan = new Scanner(System.in);

int a = scan.nextInt();

m=a/10;

n=a%10;

if (m==n){ System.out.println ("одинаковые цифры");} else {System.out.println ("разные цифры");}

}}

4.

import java.util.Scanner;
class Main {
  public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
int a = scan.nextInt();
int b = scan.nextInt();
if (a==b){System.out.println(a +" " + b);};
if (a>b){System.out.println (a+" "+b);} else {System.out.println (b+" "+a);};
}}
5.
import java.util.Scanner;
class Main {
  public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
int a = scan.nextInt();
if (9<a && a<100){System.out.println ("двузначное число");} else {System.out.println ("не двузначное число");};
}}
6.
import java.util.Scanner;
class Main {
  public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
int a = scan.nextInt();
if (a==1 || a==2 || a==12){System.out.println ("Winter");};
if (a==3 || a==4 || a==5){System.out.println ("Spring");};
if (a==6 || a==7 || a==8){System.out.println ("Winter");};
if (a==9 || a==10 || a==11){System.out.println ("Winter");};
  }}
7.
import java.util.Scanner;
class Main {
  public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
int a = scan.nextInt();
int b = scan.nextInt();
if (a>0 && b>0){System.out.println ("I quarter");};
if (a<0 && b>0){System.out.println ("II quarter");};
if (a<0 && b<0){System.out.println ("III quarter");};
if (a>0 && b<0){System.out.println ("IV quarter");};
  }}
8.
import java.util.Scanner;
class Main {
  public static void main(String[] args) {
    int d;
    int x1;
    int x2;
    Scanner scan = new Scanner(System.in);
int a = scan.nextInt();
int b = scan.nextInt();
int c = scan.nextInt();
d=b*b-4*a*c;
x1=((-1)*b+(d)^(1/2))/(2*a);
x2=((-1)*b-(d)^(1/2))/(2*a);
System.out.println(x1+" "+ x2);
  }}
10.
import java.util.Scanner;
public class Main{
    public static void main(String[] args) {
      Scanner scan = new Scanner(System.in);
 char a =scan.next().charAt(0);
  if (Character.isLetter(a)){
    System.out.println("letter");
  }
if (Character.isDigit(a)){
    System.out.println("digit");}
  }}