package main
import "fmt"

func main() {
    var n int
    var lower, lowerindex int
    fmt.Scanf("%v", &n)
    neighbours := make([]int,100)
    //saved := make([]int,n)
    for i := 0; i < n; i++ {
        fmt.Scanf("%v",&lower)
        lowerindex = lower - 1
        // if the low value of our range is equal to current, or to current - 1, then current will be counted
        neighbours[lowerindex] = neighbours[lowerindex] + 1
        if lowerindex >= 1 {
            neighbours[lowerindex - 1] = neighbours[lowerindex - 1] + 1
        }
        //fmt.Println(neighbours)
    }
    var max int
    for j := 0; j < 100; j++ {
        if neighbours[j] > max {
            //index = j + 1
            max = neighbours[j]
        }
    }
    //fmt.Println(neighbours)
    //fmt.Println("Index: ",index)
    fmt.Println(max)
    
}