#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
#include <chrono>
#include <iomanip>
#include <unordered_map>
#include <unordered_set>
#include <set>
#include <algorithm>
#include <thread>
#include <numeric>
#include <queue>
#include <functional>
#include <cmath>

using namespace std;

#define endl "\n"
#ifndef MAIN_BEGIN
#define START_TIMER(...)
#define TIMESTAMP(...)
#define MAIN_BEGIN int main() { \
    ios::sync_with_stdio(false);
#define RETURN return 0
#define MAIN_END RETURN; }
#define OUTPUT if(false) cout
#endif

MAIN_BEGIN

    int n;
    cin >> n;
    vector<int> v(n);
    for(auto& i : v) cin >> i;
    int max = 0;
    for(int x=1; x<100; x++) {
        int now = 0;
        for(auto i : v) {
            if(i == x || i == x + 1) now++;
        }
        if(now > max) max = now;
    }
    cout << max;

MAIN_END