#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);
    map<int, int> m;
    for(int a_i = 0;a_i < n;a_i++){
       cin >> a[a_i];
        m[a[a_i]]++;
    }
    int c, b;
    map<int, int> :: iterator it = m.begin();
    vector<pair<int, int> > val;
    int ans = 0;
    for(;it != m.end(); it++){
        val.push_back(make_pair(it->first, it->second));
        ans = max(ans, it->second);
    }
    //sort(val.begin(), val.end(), greater<int> ());
    //cout << val[0] + val[1] << "\n";

    for(int i = 1 ; i < val.size() - 1; i++){
        if(abs(val[i].first - val[i - 1].first) <= 1)
            ans = max(ans, val[i].second + val[i - 1].second);
        if(abs(val[i].first - val[i + 1].first) <= 1)
            ans = max(ans, val[i].second + val[i + 1].second);
    }
    cout << ans << "\n";
    return 0;
}