import java.util.LinkedHashSet;

public class Task091025 {
    public static void main(String[] args) {
        LinkedHashSet<Integer> set = new LinkedHashSet<>();
        
        set.add(1);
        set.add(2);
        set.add(3);
        set.remove(2);
        set.add(2);
        
        System.out.println(set);
    }
}

import reactor.core.publisher.Mono;

public class MonoExample {
    public static void main(String[] args) {
        Mono.just("Start")
            .doOnNext(System.out::print)
            .then(Mono.fromRunnable(() -> System.out.print("Middle")))
            .thenReturn("End")
            .subscribe(System.out::print);
    }
}

import java.util.*;

public class Task131025 {
    public static void main(String[] args) {
        Set<String> set = new HashSet<>();
        
        String s1 = "Hello";
        String s2 = new String("Hello");
        String s3 = s2.intern();
        
        set.add(s1);
        set.add(s2);
        set.add(s3);
        set.remove(s1);
        set.remove(s3);
        
        System.out.println(set.size());
        System.out.println(set.contains("Hello"));
    }
}