FastScanner.java

import java.io.*;
import java.util.StringTokenizer;

/**
 * Created by Ilya239 on 29.03.2016.
 */
public class FastScanner {
    BufferedReader br;
    StringTokenizer st;

    FastScanner(File f) {
        try {
            br = new BufferedReader(new FileReader(f));
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }

    FastScanner() {
        br = new BufferedReader(new InputStreamReader(System.in));
    }

    String next() {
        while (st == null || !st.hasMoreTokens()) {
            try {
                st = new StringTokenizer(br.readLine());
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return st.nextToken();
    }

    int nextInt() {
        return Integer.parseInt(next());
    }
}

Looper.java

import java.io.*;
import java.lang.management.ManagementFactory;
import java.util.StringTokenizer;

/**
 * Created by Ilya239 on 29.03.2016.
 */
public class Looper implements Runnable{
    static FastScanner in;
    int i = 0;
    volatile boolean done = false;

    @Override
    public void run() {
        while (!done) {
                i++;
            if (Thread.currentThread().isInterrupted()) {
                done = true;
                i = 0;
            }
        }
    }

    public static void main(String args[]) {
        int n = 3;
        try {
            in = new FastScanner();
        } catch (Exception e) {
            e.printStackTrace();
        }
        Thread[] threads = new Thread[n];
        for (int i = 0; i < n; i++) {
            threads[i] = new Thread(new Looper());
            threads[i].start();
        }
        System.out.println(Integer.parseInt(ManagementFactory.getRuntimeMXBean().getName().toString().substring(0,ManagementFactory.getRuntimeMXBean().getName().indexOf('@'))));
        try {
            PrintStream ps = new PrintStream("pid.txt");
            ps.println(ManagementFactory.getRuntimeMXBean().getName().toString().substring(0,ManagementFactory.getRuntimeMXBean().getName().indexOf('@')));
            ps.flush();
            ps.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        in.next();
        for (int i = 0; i < n; i++) {
            threads[i].interrupt();
        }

    }
}