package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

type Point struct {
	x, y int
}

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Scan(); x, _ := strconv.Atoi(sc.Text())
	sc.Scan(); y, _ := strconv.Atoi(sc.Text())
	sc.Scan(); d, _ := strconv.Atoi(sc.Text())

	if x > d {
		x = d
	}
	if y > d {
		y = d
	}
	n := (x + y) - d + 1
	if n > d + 1 {
		n = d + 1
	}
	if n < 0 {
		n = 0
	}
	fmt.Println(n)
}