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


int main() {
    int n;
    cin >> n;
    vector<int>v(n);
    for(int i = 0; i < n; i++)
            cin >> v[i];
    int ans = 0;
    for(int i = 0; i < n; i++)
    {
        vector<int>aux;
        aux.push_back(v[i]);
        
        for(int j = 0; j < n  ;j++)
        {
            if(i == j)
                   continue;
           bool put = 1;
           for(int k = 0; k < aux.size(); k++)
           {
               if(abs(aux[k] - v[j]) > 1)
                   put = 0;
           }
            if(put)
                aux.push_back(v[j]);
        }
        ans = max(ans,(int)aux.size());
       
    }
    cout << ans << '\n';
    return 0;
}