package main
import "fmt"

func main() {
    var n int
    fmt.Scanf("%d", &n)
    
    arr := make([]int, n)
    maps := make(map[int]int)
    for i:=0; i<n; i++ {
        fmt.Scanf("%d", &arr[i])
        maps[arr[i]]++
    }
    
    maxCount := 0
    for k, v := range maps {
        if (v + maps[k+1]) > maxCount {
            maxCount = v + maps[k+1]
        }
    }
    
    fmt.Println(maxCount)
}