//#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define mp make_pair
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vll;
typedef pair<int, int> pii;
typedef vector<pii> vii;
#define sz(c) (int)(c).size()
#define ALL(c) (c).begin(), (c).end()

void solve (int n)
{
    vi a(n);
    int ans = 0;
    for (int i = 0; i < n; i++)
        cin >> a[i];

    for (int x : a)
        ans = max((ll)ans, (ll)count(ALL(a), x) + (ll)count(ALL(a), x + 1));
    cout << ans << '\n';
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);

    int n;
    while (cin >> n)
        solve(n);
}