import java.util.Arrays;
import java.util.LinkedList;
import java.util.Scanner;

public class Main {
	
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		final long x = sc.nextLong();
		final long y = sc.nextLong();
		final long d = sc.nextLong();
		
		System.out.println(Math.max(0, (d + 1) - Math.max(0, d - x) - Math.max(0, d - y)));
	}
	
}