import java.util.Scanner;
import java.util.concurrent.*;
class Numbers {
public static Callable<Integer> consecutiveSum(int start, int end) {
// write your code here
return null;
}
// Don't change the code below
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int start = scanner.nextInt();
int end = scanner.nextInt();
ExecutorService executorService = Executors.newSingleThreadExecutor();
Future<Integer> future = executorService.submit(consecutiveSum(start, end));
int result = 0;
try {
result = future.get();
} catch (InterruptedException | ExecutionException e) {
e.printStackTrace();
}
executorService.shutdown();
System.out.println(result);
}
}
