#include <map>
#include <set>
#include <list>
#include <cmath>
#include <ctime>
#include <deque>
#include <queue>
#include <stack>
#include <string>
#include <bitset>
#include <cstdio>
#include <limits>
#include <vector>
#include <climits>
#include <cstring>
#include <cstdlib>
#include <fstream>
#include <numeric>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <unordered_map>

using namespace std;
int max_pos(int a , int b)
    {
       if(a>b) return a;
       else return b;
    }

int main(){
    int n;
    cin >> n;
    int a[n];
    int i,j,count,max=0,pos,neg;
    for(i=0;i<n;i++)
        cin>>a[i];
    
    for(i=0;i<n;i++)
        {
          count=0,pos=0,neg=0;
        for(j=0;j<n;j++)
            {
               if(a[j]==a[i]+1) pos++;
               else if(a[j]==a[i]-1) neg++;
                  else if(a[i]==a[j]) count++;
            }
           //cout<<pos<<" "<<neg<<" ";
           count+=max_pos(pos,neg);//cout<<count<<" ";
           if(max<count)
              max=count;
            //cout<<max<<endl;          
        }
          
        
   cout<<max<<endl;
    return 0;
}