package main

import (
	"fmt"
	"math"
)

func AbsInt(x int) int {
	return int(math.Abs(float64(x)))
}

func resolve(A, B, S int) int {
	ret := S
	if AbsInt(A-S) <= AbsInt(B-S) {
		// Move A
		return ret + AbsInt(A-S)
	}
	// Move B + A (goto 1st floor)
	if A == 0 {
		ret += 1
	} else {
		ret += A - 1
	}
	return ret + AbsInt(B-S)
}

func main() {
	var A, B, S int

	fmt.Scanf("%d %d %d\n", &A, &B, &S)

	fmt.Println(resolve(A, B, S))
}