#include <bits/stdc++.h>
time_t t=clock();
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<ll> vll;
#define mp make_pair
#define rep(i,n) for(ll i = 0; i < n; i++)
#define rep1(i,a,b) for(ll i = a; i <= b; i=i++)
#define rep2(i,b,a) for(ll i=b; i>=a ;i--)
#define F first
#define S second
#define pb push_back
#define mod 1000000007
int main(){
	ll arr[100]={0};
	
	ll n;
	cin>>n;
	rep(i,n){
		ll a;
		cin>>a;
		arr[a]++;
	}
	ll mx=0;
	for(ll i=1;i<100;i++){
		if(arr[i]+arr[i-1]>mx)
		mx=arr[i]+arr[i-1];
	}
	cout<<mx;
 // cout<<"time"<<(double)(clock()-t)/CLOCKS_PER_SEC;
   return 0;
}