import java.util.*;
import java.util.concurrent.*;
import java.lang.*;
 
public class Main {
 
public Main() {
    ExecutorService es = Executors.newCachedThreadPool();
    for (int i = 0; i < 20; i++) {
        es.execute(new Runnable() {
            @Override
            public void run() {
                synchronized (lock) {
                    sum += 1;
                }
            }
        });
    }
    es.shutdown();
    while(!es.isTerminated()) {
    }
}
private int sum = 0;
private final Object lock = new Object();
 
public static void main(String[] args) {
    Main t = new Main();
    System.out.println(t.sum);
}
}

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