ProgBasicsExam16December2018-E05Bus2

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        int passengers = Integer.parseInt(scanner.nextLine());
        int stops = Integer.parseInt(scanner.nextLine());
        int counter = 0;
        int i = 0;

        while (i < stops) {
            i++;
            int passengersOut = Integer.parseInt(scanner.nextLine());
            int passengersIn = Integer.parseInt(scanner.nextLine());
            passengers -= passengersOut;
            passengers += passengersIn;
            counter++;

            if (counter % 2 == 0) {
                passengers -= 2;
            } else {
                passengers += 2;
            }
        }
        System.out.printf("The final number of passengers is: %d.", passengers);

    }
}