import java.util.Scanner;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner koko = new Scanner(System.in);
       int x = koko.nextInt();
       int y = koko.nextInt();
       int d = koko.nextInt();
       int point;
       if(d>x+y){
           point = 0;
       }else if(x<y){
           if(d<x){
               point=d+1;
           }else if(x<=d&&d<=y){
               point=x+1;
           }else{
               point = x+y+1-d;
           }
       }else{
           if(d<y){
               point=d+1;
           }else if(y<=d&&d<=x){
               point = y+1;
           }else{
               point = x+y+1-d;
           }
       }
       
       System.out.println(point);
    }
}