fun main(args:Array<String>) {
    val (a,b,s) = readLine()!!.split(" ").map { it.toInt() }
    println(getAns(a,b,s))
}

fun getAns(a:Int, b:Int, s:Int):Int {
    if(s == 1) {
        if(a == 0) {
            return 2
        } else {
            return a
        }
    }
    if(Math.abs(a-s) > Math.abs(b-s)) {
        return getAns(a, s, 1) + Math.abs(b-s) + (s - 1)
    }
    return Math.abs(a-s) + s
}