#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,i,j,best = -1,count = 1;
    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());
    for(i = 0; i < n - 1; i++){
        for(j = i+1; j < n; j++){
            if(abs(a[j]-a[i]) <= 1){
                count++;
            }
        }
        if(count > best) best = count;
        count = 1;
    }
    if(best == -1) cout << 2;
    else cout << best;
    return 0;
}