#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

void sort(int a[],int n);
int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int n,i,j,len,max=0;
    cin>>n;
    int a[n];
    //input the array
    for(i=0;i<n;i++)
        cin>>a[i];
    //sort the array
    sort(a,n);
    //displaying the sorted array
    /*for(i=0;i<n;i++)
        cout<<a[i]<<" ";
    cout<<endl;*/
    //main operation
    for(i=0;i<n;i++)
    {
        len = 1;
        for(j=i+1;j<n;j++)
        {
            if((a[j]-a[i])<=1)
                len++;
            else
                break;
        }
        if(len>max)
            max = len;
    }
    cout<<max;
    return 0;
}

void sort(int a[],int n)
{
    int i,j,k;
    for(i=1;i<n;i++)
    {
        k = a[i];
        for(j=i-1; j>=0 && a[j]>k; j--)
            a[j+1] = a[j];
        a[j+1] = k;
    }
}