#include <math.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include <limits.h>
#include <stdbool.h>

int main(){
    int n,max,i,count1,count2; 
    scanf("%d",&n);
    int *a = malloc(sizeof(int) * n);
    for(i = 0; i < n; i++){
       scanf("%d",&a[i]);
    }
    int b[n];
    for(i=0;i<n;i=i+1)
        {
        count1=0,count2=0;
        for(int j=0;j<n;j=j+1)
            {
            if(a[j]==a[i]-1||a[j]==a[i])
                {
                count1=count1+1;
            }
            if(a[j]==a[i]+1||a[j]==a[i])
                {
                count2=count2+1;
            }
        }
        if(count1>count2)
            {
            b[i]=count1;
        }
        else
            {
            b[i]=count2;
        }
    }
    max=b[0];
    for(i=0;i<n;i=i+1)
        {
        if(b[i]>max)
            {
            max=b[i];
        }
     //   printf("%d",b[i]);
    }
   printf("%d",max);
    return 0;
}