#include <bits/stdc++.h>
using namespace std;

#define pb push_back
#define mp make_pair

typedef long long ll;
typedef pair<int, int> pii;

int n;
int cnt[100];

int main() {
#ifdef LOCAL
  freopen("input.txt", "r", stdin);
  freopen("output.txt", "w", stdout);
#endif
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cin >> n;
  for (int i = 0, a; i < n; ++i) {
    cin >> a;
    ++cnt[a];
  }
  int res = 0;
  for (int i = 0; i < 99; ++i) {
    res = max(res, cnt[i] + cnt[i + 1]);
  }
  cout << res << endl;
  return 0;
}