import java.util.*;
public class Distance {
	public static void main(String[] arg){
		Scanner sc = new Scanner(System.in);
		int x,y,d,res,temp;
		x = sc.nextInt();
		y = sc.nextInt();
		d = sc.nextInt();
		if(d<x){
			if(d<y){
				res = d+1;
			}else{
				res = y + 1;
			}
		}else{
			if(d<y){
				res = x + 1;
			}else{
				res = x + y + 1 - d;
				if(res < 0)res = 0;
			}
		}
		System.out.println(res);
	}
}