import java.math.*;
import java.util.*;

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