package no131;

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int x = sc.nextInt();
		int y = sc.nextInt();
		int d = sc.nextInt();
		System.out.println(solve(x,y,d));
	}

	public static long solve(long x,long y,long d) {
		if (d > x + y) {
			return 0;
		}
		long right = d <= x ? d : x;
		long left = d <= y ? 0 : d - y;
		return right - left + 1;
	}

}