#include <bits/stdc++.h>
using namespace std;
int main(){
  int N;
  cin >> N;
  vector<int> A(N);
  for (int i = 0; i < N; i++){
    cin >> A[i];
  }
  map<int, int> mp;
  for (int i = 0; i < N; i++){
    mp[A[i]]++;
  }
  int ans = 0;
  for (int i = 0; i < N; i++){
    ans = max(ans, mp[A[i] - 1] + mp[A[i]]);
    ans = max(ans, mp[A[i]] + mp[A[i] + 1]);
  }
  cout << ans << endl;
}