import java.util.concurrent.*;
class MutableInteger {
	private int value;
	public int getValue(){
		return value;
	}
	public void setValue(int value){
		this.value = value;
	}
}
class Summation implements Runnable{
	private int upper;
	private MutableInteger sumValue;
	public Summation(int upper, MutableInteger sumValue){
		this.upper = upper;
		this.sumValue = sumValue;
	}
	public void run(){
		int sum=0;
		for(int i=0;i<= upper; i++)
			sum += i;
		sumValue.setValue(sum);
	}
}
public class Driver{
	public static void main(String[] args) {
		if(args.length>0){
			if(Integer.parseInt(args[0])< 0)
				System.err.println(args[0]+"must be >=0.");
			else{// create the object to be shared
				MutableInteger sum=new MutableInteger();
				int upper = Integer.parseInt(args[0]);
				Thread thrd = new Thread(new Summation(upper, sum));
				thrd.start();
				try{
					thrd.join();		
					System.out.println("The sum of "+upper+" is "+sum.getValue());
				}
				catch(InterruptedException ie) {}
				}
		}
		else
			System.err.println("Usage:Summation <integer value>");
	}

}