#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    int N;
    cin >> N;
    vector<int> v;
    v.reserve(N);
    while(N-->0)
    {
        int val;
        cin >> val;
        v.push_back(val);
    }

    std::sort(v.begin(),v.end());

    int r = 0;

    for(int i = 0; i < v.size(); ++i)
    {
        int t = 1;

        for(int j = i+1; (j < v.size()) && (abs(v[i] - v[j]) <= 1); ++j) ++t;

        r = max(r,t);

    }

    cout << r << endl;


    return 0;
}