#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;
    map<int,int> mymap;
    vector<int> a(n);
    for(int a_i = 0;a_i < n;a_i++){
       cin >> a[a_i];
        mymap[a[a_i]]++;
    }
    int max=0;
    
   // for(map<int,int> :: iterator it=mymap.begin();it!=mymap.end();++it){
     //   cout<<it->first<<" "<<it->second<<endl;
    //}
    
    
    for(int i=1;i<=100;i++){
        if(max < mymap[i]+mymap[i+1])
            max=mymap[i]+mymap[i+1];
    }
    
    
/*    
    for(map<int,int> :: iterator it=mymap.begin();it!=mymap.end();++it){
        cout<<"$"<<it->first <<"$"<<endl;  
        if(max < ((it->second) + mymap[(it->first)+1])){
               max=(it->second) + mymap[(it->first)+1];
               cout<<max<<" "<<" "<<it->first<<endl;
           }
        cout<<"@"<<endl;
        if(it==mymap.end())
            break;
    }
*/
    cout<<max<<endl;
    
    return 0;
}