#include <bits/stdc++.h>

using namespace std;

int main()
{
    int n , mx = 0 , a , b;

    cin >> n;

    map < int , int > mp;
    map < int , int > :: iterator it;

    vector < pair < int , int > > vp;

    for(int i = 0 ; i < n ; i++)
    {
        int c;
        cin >> c;

        mp[c]++;
    }

    int i = 0;
    for(it = mp.begin() ; it != mp.end() ; it++)
    {
        if(it->second > mx) mx = it->second;
    }

    for(it = mp.begin() ; it != mp.end() ; it++)
    {
        if(i != 0)
        {
            if(abs(it->first - a) <= 1)
            {
                if(mx < it->second + b)
                {
                    mx = it->second + b;
                }
            }
        }

        a = it->first;
        b = it->second;

        i++;
    }

    cout << mx << endl;

    return 0;
}