import java.util.Scanner;

public class BarefootProgram {
	public static void main(String[] args) {
		int		numKids, withSocks, withShoes, withBoth;
		Scanner		keyboard = new Scanner(System.in);

		// Get the user input
		System.out.println("How many kids are there ? ");
		numKids = keyboard.nextInt();

		System.out.println("How many are wearing socks ? ");
		withSocks = keyboard.nextInt();

		System.out.println("How many are wearing shoes ? ");
		withShoes = keyboard.nextInt();

		System.out.println("How many are wearing both shoes and socks ? ");
		withBoth = keyboard.nextInt();

		// Now compute the answer
		int socksOnly = withSocks - withBoth;
		int shoesOnly = withShoes - withBoth;
		int barefoot = numKids - withBoth - socksOnly - shoesOnly;

		// Finally, display the results nicely
		System.out.println("There are " + barefoot + " barefoot kids.");
    }
}