#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>
#include <bits/stdc++.h>

using namespace std;


int main(){
    int n;
    cin >> n;
    int arr[n];
    for(int a_i = 0;a_i < n;a_i++){
       cin >> arr[a_i];
    }
    sort(arr,arr+n);
    int index=0;
    int count,max=0;
    while(index<n){
        count=1;
        for(int i=index;i<n-1;i++){
            if(arr[i+1]-arr[index]<=1){
                count++;
                //cout<<arr[i];
            }
            else{
                break;
                
            }
        }//cout<<endl;
        if(count>max && (!(count==1))){
            max=count;
        }
        index++;
    }
    //cout<<endl;
    cout<<max;
    return 0;
}