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);
    }
  }
}