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;
		}
		int dis = d - y;
		for (int i = 0; i <= x; i++) {
			if (dis <= i)
				count += 1;
		}
		System.out.println(count);
	}
}