#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 N;
int occ[105];

int main()
{
    cin >> N;
    for (int i = 0, a; i < N; i++)
    {
        cin >> a;
        occ[a]++;
    }
    
    int ans = 0;
    for (int i = 1; i <= 99; i++)
        ans = max(ans, occ[i] + occ[i + 1]);
    
    cout << ans << "\n";
    
    return 0;
}