import java.util.*;
public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int a = sc.nextInt();
		int b = sc.nextInt();
		int s = sc.nextInt();
		int mva = Math.abs(a-s);
		int mvb = Math.abs(b-s);
		int sum = 0;

		if(mva <= mvb){
			// aの方が近い
			sum += mva + s;
		}else{
			// bの方が近い
			if(a == 0 && mva != mvb){
				a++;
				sum++;
			}

			if(mva >= s){
				sum += mvb + (s-1) + a;
			}else{
				sum += mvb + mva + a;
			}
		}
		System.out.println(sum);
	}
}