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

typedef long long ll;
typedef vector<int> vi;
typedef pair<int,int> ii;

#define fill(a,x) memset(a,x,sizeof(a)) 
#define pb push_back
#define sz(x) (int)x.size() 
#define F first
#define S second
#define FOR(i,a,b) for(int i = a; i<=b; ++i)
#define NFOR(i,a,b) for(int i = a; i>=b; --i)
#define fast ios_base::sync_with_stdio(false),cin.tie(0),cout.tie(0)
const ll INF = 1e18;
const ll mod = 1e9+7;
const int N = 1e5+10; 

int arr[110];
int main(){
  fast;
  int n;
  cin>>n;
  FOR(i,1,n)
  cin>>arr[i];

  int ans=2;
  int count=0;
  for(int i=1;i<100;i++)
  {
  	count=0;
  	for(int j=1;j<=n;j++)
  	if(arr[j]==i or arr[j]==i+1)
  	count++;
  	
  	if(count>ans)
  		ans=count;
  }

  cout<<ans;
  return 0;
}