#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 res = 0;
    int current = 1;
    int s = 0;
    int e = 0;
    for(int i = 0; i < n-1; i++) {
        if(a[i+1] - a[s] <= 1 && a[i+1] - a[e] <= 1) {
            e++;
        } else {
            if(e - s + 1 > res) res = e - s + 1;
            s = i+1;
            e = i+1;
        }
    }
    if(e - s + 1 > res) res = e - s + 1;
    cout << res << endl;
    return 0;
}