package main

import . "fmt"

func main() {
	var n int
	Scan(&n)
	t:=make([]int,36,36)
	for ;n>0;n-- {
		var a int
		Scan(&a)
		t[a]++
	}
	s:=0
	for i,c:=range t[1:] {
		if t[i]==0 {
			s+=c*(i+1)
		}
	}
	Println(s)
}