// Sum4.java

import java.math.BigInteger;

class SumThread extends Thread {
    private BigInteger from, to, sum;
    
    public SumThread(BigInteger from, BigInteger to) {
        this.from = from;
        this.to = to;
        sum = new BigInteger("0");
    }

    @Override
    public void run() {
        BigInteger one = new BigInteger("1");
        for (BigInteger i = from; i.compareTo(to) <= 0; i = i.add(one)) {
            sum = sum.add(i);
        } 
    }

    public BigInteger getSum() {
        return sum;
    }
}


public class Sum4 {
    public static void main(String args[]) {
        if (args.length != 3) {
            System.out.println("Pass threads, start and end.");
            return;
        }

        // get arguments
        int num_threads = Integer.parseInt(args[0]);
        BigInteger from = new BigInteger(args[1]);
        BigInteger to = new BigInteger(args[2]);

        // an array of threads
        SumThread [] threads = new SumThread[num_threads];

        //  fill in the start/end ranges for each
        BigInteger step = to.subtract(from).divide(BigInteger.valueOf(num_threads));
        for (int i = 0; i< num_threads; i++) {
            BigInteger start = from.add(step.multiply(BigInteger.valueOf(i)));
            BigInteger stop = start.add(step).subtract(BigInteger.valueOf(1));

            // make sure we go all the way to the end on last thread
            if (i == (num_threads - 1)) {
                stop = to;         
            }

            System.out.printf("Thread %s sums from %s to %s.\n", i, start.toString(), stop.toString());
            threads[i] = new SumThread(start, stop);
        }

        // start them all
        for (int i = 0; i< num_threads; i++) {
            threads[i].start();
        }

        // wait for all the threads to finish!
        try {
            for (int i = 0; i< num_threads; i++) {
                threads[i].join();
            }
        } catch (InterruptedException e) {
            System.out.println("Interrupted");
        }

        // calculate total sum
        BigInteger total_sum = new BigInteger("0");
        for (int i = 0; i < num_threads; i++) {
            total_sum = total_sum.add(threads[i].getSum());
        }

        System.out.printf("The sum of %s-%s is %s.\n", from.toString(), to.toString(), total_sum.toString());
    }
}