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

#define pb push_back
#define mk make_pair
#define ff first
#define ss second
#define INF 1000000000000000000LL
#define MOD 1000000007
#define EPS 1e-6
typedef long long ll;

ll Pow(ll a, ll b){

  if(b==0) return 1;

  ll p=Pow(a,b/2);
  p = p*p;
  if(b&1){
    p = (p*a);
  }
  return p;
}

int main(){

  int n;
  cin>>n;
  vector<int> arr(100, 0);

  for(int i=0; i<n; i++){

    int x;
    cin>>x;
    arr[x]++;
  }

  int ans=0;

  for(int i=1; i<=98; i++){

    if(arr[i]+arr[i+1]>ans){

      ans=arr[i]+arr[i+1];
      //cout<<ans<<" "<<i<<'\n';
    }
  }
  cout<<ans;
  return 0;
}