import java.util.*;
public class Distance{
	public static void main(String... args){
		Scanner scan = new Scanner(System.in);
		int x = scan.nextInt();
		int y = scan.nextInt();
		int d = scan.nextInt();
		if(x+y<d){
			System.out.println(0);
			return;
		}
		int dx = (d <= x)? d:x;
		int dy = (d <= y)? d:y;
		System.out.println(1+dx-dy);
	}
}