#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,c,d,swap;
scanf("%d",&n);
int arr[n],i,count[n],j,max1=-999999;
for(i= 0; i< n; i++)
{
scanf("%d",&arr[i]);
}
for (c = 0 ; c < ( n - 1 ); c++)
{
for (d = 0 ; d < n - c - 1; d++)
{
if (arr[d] > arr[d+1])
{
swap = arr[d];
arr[d] = arr[d+1];
arr[d+1] = swap;
}
}
}
for(i=0;i<n-1;i++)
{count[i]=0;
for(j=i;j<n;j++)
{
if(arr[j]==arr[i]||(arr[j]-arr[i])==1)
count[i]++;
}
if(count[i]>max1)
max1=count[i];
}

printf("%d",max1);
return 0;
}