package main

import (
	"bufio"
	"bytes"
	"fmt"
	"os"
	"sort"
)

func main() {
	n := readi()
	a := readis(n)
	sort.Ints(a)
	fmt.Fprintln(writer, solve(a))
	writer.Flush()
}

func solve(a []int) int {
	res := 0
	for i := range a {
		count := 0
		for j := i; j < len(a); j++ {
			if a[j]-a[i] > 1 {
				break
			}
			count++
		}
		res = max(res, count)
	}
	return res
}

var (
	reader = bufio.NewReaderSize(os.Stdin, 1<<13)
	writer = bufio.NewWriterSize(os.Stdout, 1<<13)
)

func abs(a int) int {
	if a < 0 {
		return -a
	}
	return a
}

func abs64(a int64) int64 {
	if a < 0 {
		return -a
	}
	return a
}

func max(a, b int) int {
	if a > b {
		return a
	}
	return b
}

func max64(a, b int64) int64 {
	if a > b {
		return a
	}
	return b
}

func min(a, b int) int {
	if a < b {
		return a
	}
	return b
}

func min64(a, b int64) int64 {
	if a < b {
		return a
	}
	return b
}

func readi() int {
	return int(readi64())
}

func read2i() (int, int) {
	return readi(), readi()
}

func readis(n int) []int {
	res := make([]int, n)
	for i := range res {
		res[i] = readi()
	}
	return res
}

func readi64() int64 {
	b, err := reader.ReadByte()
	for !isValid(b, err) {
		b, err = reader.ReadByte()
	}
	sign, res := int64(1), int64(0)
	if b == '-' {
		sign *= -1
		b, err = reader.ReadByte()
	}
	for isValid(b, err) {
		res = res*10 + int64(b-'0')
		b, err = reader.ReadByte()
	}
	return res * sign
}

func readline() string {
	res := new(bytes.Buffer)
	for {
		line, isPrefix, err := reader.ReadLine()
		if err != nil {
			panic(err)
		}
		res.Write(line)
		if !isPrefix {
			break
		}
	}
	return res.String()
}

func isValid(b byte, err error) bool {
	return err == nil && (('0' <= b && b <= '9') || b == '-')
}