using System;
using System.Collections;
using System.Collections.Generic;
 
class TEST{
	static void Main(){
		Sol mySol =new Sol();
		mySol.Solve();
	}
}

class Sol{
	public void Solve(){
		
		if(Y>X){
			long t=Y;Y=X;X=t;
		}
		if(D<=Y){
			Console.WriteLine(D+1);return;
		}
		if(D<=X){
			Console.WriteLine(Y+1);return;
		}
		if(D<=X+Y){
			Console.WriteLine(Y-(D-X)+1);return;
		}
		Console.WriteLine(0);return;
		
		
	}
	long X,Y,D;
	public Sol(){
		var d=rla();
		X=d[0];Y=d[1];D=d[2];
	}




	static String rs(){return Console.ReadLine();}
	static int ri(){return int.Parse(Console.ReadLine());}
	static long rl(){return long.Parse(Console.ReadLine());}
	static double rd(){return double.Parse(Console.ReadLine());}
	static String[] rsa(){return Console.ReadLine().Split(' ');}
	static int[] ria(){return Array.ConvertAll(Console.ReadLine().Split(' '),e=>int.Parse(e));}
	static long[] rla(){return Array.ConvertAll(Console.ReadLine().Split(' '),e=>long.Parse(e));}
	static double[] rda(){return Array.ConvertAll(Console.ReadLine().Split(' '),e=>double.Parse(e));}
}