package main

import (
	"fmt"
	"math"
	"sort"
)

func MaxInt(x, y int) int {
	return int(math.Max(float64(x), float64(y)))
}

func MinInt(x, y int) int {
	return int(math.Min(float64(x), float64(y)))
}

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

func SortInt(d []int) {
	sort.Sort(sort.IntSlice(d))
}

func resolve(A, B, S int) int {
	if A >= S {
		return A
	}
	if AbsInt(S-A) <= AbsInt(B-S) {
		return S - A + S
	}
	if A == 0 {
		return B - S + S + 1
	}
	return B - S + S
}

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

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

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