import java.util.Scanner;

public class Main {
	public static void main(String[] a) {
		Scanner s = new Scanner(System.in);
		int x=s.nextInt(),y=s.nextInt(),d=s.nextInt();
		System.out.println(d>x+y?0:(x>d?d:x)-(y>d?0:d-y)+1);
	}
}