#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];
    }

	sort(a.begin(), a.end());

	int flag=0;
	int count = 0;
	int count1 = 0;
    int count2 = 0;
    int prev = a[0];
	for(int i = 0;i < n;i++)
	{
       //cout<<count<<" "<<count2<<endl;

		if(a[i] - prev <=1 )
            {
            count++;
        }
        else
        {
            prev = a[i];
            if(count2<count) count2 = count;
            count = 1;
        }

	}
    if(count2<count) count2 = count;
	cout<<count2;
    
    return 0;
}