#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);
    for(int a_i = 0;a_i < n;a_i++){
       cin >> a[a_i];
    }
    map<int, int> m;
    map<int, int>::iterator it, it1;
    for(int i=0;i<n;i++){
        m[a[i]]++;
    }
    vector<int> v;
    if(m.size() == 1){
        cout<<m[a[0]]<<"\n";
    }else{
        int max_ans=m.begin()->second;
        it = m.begin();
        it++;
        it1 = m.begin();
        for(;it!=m.end();it++){
            if(it->first-it1->first == 1){
                if(it->second+it1->second > max_ans){
                    max_ans = it->second+it1->second;
                }
            }else if(it->second > max_ans){
                max_ans = it->second;
            }
            it1 = it;
        }
        cout<<max_ans<<"\n";
    }
    return 0;
}