import java.util.*; public class Exercise98{ 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 smaller = Math.min(x, y); int bigger = Math.max(x, y); if(d < smaller){ System.out.println(d - 1 + 2); }else if(d >= smaller && d <= bigger){ System.out.println(smaller - 1 + 2); }else if(d < bigger + smaller){ System.out.println((bigger + smaller - d) - 1 + 2); }else{ System.out.println(0); } } }