package main

import . "fmt"
import . "sort"

func main() {
	var n int
	Scan(&n)
	a:=make([]int,n)
	for i:=range a {
		Scan(&a[i])
	}
	Ints(a)
	for i,v:=range a[1:] {
		if a[i]+1==v {
			Println(2)
			return
		}
	}
	Println(1)
}