package main

import . "fmt"

func main() {
	var x,y,d int64
	Scan(&x,&y,&d)
	cnt := d+1
	if y < d {
		cnt -= d-y
	}
	if x < d {
		cnt -= d-x
	}
	if cnt < 0 {
		cnt = 0
	}
	Println(cnt)
}