package main

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

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())

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