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

int main()
{
  int n;
  cin>>n;

  int arr[n];
  for(int i = 0; i < n; i++) cin>>arr[i];

  sort(arr,arr+n);
  unsigned long long ans = 0, cnt = 0;

  for(int i = n - 1; i >= 0; i--)
  {
     for(int j = i - 1; j >= 0; j--)
     {
        if(arr[i] - arr[j] == 0 || arr[i] - arr[j] == 1)
        {
           cnt++;
        }
        else break;
     }

     ans = max(ans,cnt);

     cnt = 0;
  }
  cout<<ans+1<<endl;

  return 0;
}