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();
        int count=d+1;
        if(x < d)count -= d - x;
        if(y < d)count -= d - y;
        if(x+y<d){System.out.println(0);return;}
        System.out.println(count);
    }
}