#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 main(){
    int n;
    cin >> n;
    vector<int> a(n);
    for(int a_i = 0;a_i < n;a_i++){
       cin >> a[a_i];
    }
    sort(a.begin(),a.end());
    
    vector <int> countp(n);
    vector <int> countn(n);
    countp={0};
    countn={0};
    
    for (int i=0;i<n;i++)
        {
          int j=i;
          while((a[j]-a[i]==0 || a[j]-a[i]==1) && j<n)
              {
              countp[i]++;
              
              j++;
          }
          int k=0;
          while((a[i]-a[k]==0 ||a[i]-a[k]==1) && k<=i)
              {
              countn[i]++;
              k++;
          }
    }
        
        int max1=countp[0];
          for(int i=0;i<n;i++)
            {
              if(countp[i]>max1)
                  {max1=countp[i];}
           }
      int max2=countn[0];
          for(int i=0;i<n;i++)
              {
               if(countn[i]>max2)
                   {max2=countn[i];}
              }
    
        
        if(max1>max2)
            {
            
            cout<<max1;
        }
       else
          {
            
            cout<<max2;
       }
        
    return 0;
}