import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int x = scan.nextInt();
		int y = scan.nextInt();
		int d = scan.nextInt();
		scan.close();
		if(x + y < d) {
			System.out.println(0);
			System.exit(0);
		}
		if(x >= d && y >= d) {
			System.out.println(d + 1);
		}else if(x < d && y >= d) {
			int ans = d + 1 - (d - x);
			System.out.println(ans);
		}else if(x >= d && y < d) {
			int ans = d + 1 - (d - y);
			System.out.println(ans);
		}else {
			int ans = d + 1 - (d - x) - (d - y);
			System.out.println(ans);
		}

	}
}