#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,p;
    cin >> n;
    //vector<int> a(n);
    map<int,int> hasmap;
    for(int a_i = 0;a_i < n;a_i++){
       cin >>p;
        hasmap[p]++;
    }
    int sum=0,maxsum=0;
    auto it = hasmap.begin();
    auto itp = it;
    
    sum = maxsum = it->second;
    it++;
    for(;it!= hasmap.end();it++){
        if(it->first - itp->first <=1)  sum = it->second+itp->second;
        else sum = max(it->second,itp->second);
        if(maxsum<sum) maxsum=sum;
        itp = it;
    }
    cout<<maxsum;
    return 0;
}