#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,ar[109],ans=-99,idx=0,as=-99;
    cin >> n;
    vector<int> a(n);
    for(int i=0;i<101;i++)ar[i]=0;
    for(int a_i = 0;a_i < n;a_i++){
       cin >> a[a_i];
        ar[a[a_i]]++;
    }
    for(int i=1;i<=99;i++)
        {
        if(ar[i]>=ans)
            {
            ans= max(ans,ar[i]);
            as = max(as,ar[i]+max(ar[i-1],ar[i+1]));
        }
    }
    cout << as;
    return 0;
}