#include<bits/stdc++.h>
using namespace std;
typedef pair<int,int> pii;
typedef pair<long long,long long> pll;
typedef vector<int> vi;
typedef pair<double,double> pdd;
typedef vector<long long> vll;
typedef vector<pii> vpii;
typedef vector<pll> vpll;
typedef vector<pdd> vpdd;
 
#define f first
#define s second
#define mp make_pair
#define pb push_back
#define MOD 1000000007
#define ll long long
ll GCD(ll a, ll b)
{
    return b? GCD(b,a%b) : a;
}
bool chk(string first, string second)
{
    string t1 = first + second;
    string t2 = second + first;
    return t1 < t2;
}
struct sort_pred
{
    bool operator()(const pair<int,int> &left, const pair<int,int> &right)
    {
        return left.second < right.second;
    }
};
long long POW(long long Base, long long Exp)
{
    long long y,ret=1;
    y=Base;
    while(Exp)
    {
        if(Exp&1)
            ret=(ret*y)%MOD;
        y = (y*y)%MOD;
        Exp/=2;
    }
    return ret%MOD;
}
 
vll A,B,C,D,Res,Mark;
string str2,str1,s1,s2;
set<string> st;
stack<ll> chlo;
vpll Rec;
string ItoS(ll n)
{
	ll num = n;
	ll tmp;
	string ans ="";
	while(num)
	{
		tmp = num%10;
		ans = ans + (char)('0'+tmp);
		num/=10;
	}
	reverse(ans.begin(),ans.end());
 
	return ans;
}
int cont(ll n)
{
  	ll count = 0;
  	while(n)
  	{
    	count += n & 1;
    	n >>= 1;
  	}
  	return count;
}
set<ll> At,Bt;
set<ll>::iterator itr;
vector<string> kyu,andar,bahar;
#define itfr(it,stl) for(it=stl.begin();it!=stl.end();it++)

map <pll, ll> Reg;
map<ll,ll> ::iterator it;
vector<vll> Graph;
ll mark[107];
int main()
{
    ll i,j,k,l,m,n,x,y,z,t,tmp1,tmp2,tmp3,ind,Max,d1,d2;
    
    //cin>>t;
    //while(t--)
    {
    	cin>>n;
		A.resize(n);
		B.resize(101);
		for(i=0; i<n; i++)
		{
			cin>>A[i];
			mark[A[i]]++;
		}
		
		z = 0;
		
		for(i=1; i<100; i++)
		{
			z = max(z, mark[i] + mark[i+1]);
		}
		cout<<z<<endl;
    }
   	return 0;
}