#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;
    unordered_map<int, int> ends = unordered_map<int, int>();
    int maximum = 0;
    for(int a_i = 0;a_i < n;a_i++){
        int temp;
       cin >> temp;
        if (ends.find(temp+1) != ends.end()){
            ends[temp+1]++;
        }
        else {
            ends[temp+1]=1;
        }
        
        if (ends.find(temp) != ends.end()){
            ends[temp]++;
        }
        else {
            ends[temp]=1;
        }
        
        if (ends[temp] > maximum) maximum = ends[temp];
        if (ends[temp+1] > maximum) maximum = ends[temp+1];
        

    }
    
    cout << maximum << endl;
    return 0;
}