import java.util.Scanner;

public class No_103 {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int x = sc.nextInt();
		int y = sc.nextInt();
		int d = sc.nextInt();
		int count = 0;
		if (x + y < d) {
			System.out.println(count);
			return;
		}
		if (x + y == d) {
			System.out.println(1);
			return;
		}
		int tx = 0;
		int ty = 0;
		count = d + 1;
		if (x < d)
			count -= (d - x);
		if (y < d)
			count -= (d - y);

		System.out.println(count);
	}
}