using static System.Math;
using System;

public class Hello
{
    public static void Main()
    {
        string[] line = Console.ReadLine().Trim().Split(' ');
        var a = int.Parse(line[0]);
        var b = int.Parse(line[1]);
        var s = int.Parse(line[2]);
        var ans = getAns(a, b, s);
        Console.WriteLine(ans);
    }
    public static int getAns (int a, int b, int s)
    {
        if (s == 1 && a == 0) return 2;
        if (s == 1 && a > 0) return a;
        var a1 = Abs(a - s);
        var b1 = Abs(b - s);
        if (a1 <= b1) return a1 + s;
        else return b1 + s + Abs(a - 1);
    }
}