#include <bits/stdc++.h>
using namespace std;
typedef  long long ll;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef vector<ll> vll;
int inf_int=1e9;
ll inf_ll=2e18;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
#define pb push_back
const double pi=3.1415926535898;
#define dout if(debug) cout
#define fi first
#define se second
#define sp setprecision
#define sz size()


template<typename T,typename T1>
void prin(vector<pair<T,T1> >& a)
{
    for(int i=0;i<a.size();i++)
    {
        cout << a[i].fi<<" "<<a[i].se<<"\n";
    }
}

template<typename T,typename T1>
void prin(set<pair<T,T1> >& a)
{
    for(auto it=a.begin();it!=a.end();it++)
    {
        cout <<it->fi <<" "<<it->se<<"\n";
    }
}
template<typename T>
void prin(vector<T>& a)
{
    for(int i=0;i<a.size();i++)
    {
        cout << a[i];
        if(i<a.size()-1)
            cout<<" ";
        else
            cout <<"\n";
    }
}
template<typename T>
void prin(set<T>& a)
{
    for(auto it=a.begin();it!=a.end();it++)
    {
        cout << *it<<" ";
    }
}
template<typename T>
void prin_new_line(vector<T>& a)
{
    for(int i=0;i<a.size();i++)
    {
        cout << a[i]<<"\n";
    }
}
template<typename T,typename T1>
void prin_new_line(vector<pair<T,T1> >& a)
{
    for(int i=0;i<a.size();i++)
    {
        cout << a[i].fi<<" "<<a[i].se<<"\n";
    }
}

bool debug=0;
const int maxn=1e5+10;
int mod=1e9+7;



void solve()
{
    int n;
    cin >> n;
    map<int,int> mp;
    vector<int> a;
    for(int i=1;i<=n;i++)
    {
        int x;
        cin >> x;
        a.pb(x);
        mp[x]++;
    }
    int ans=0;
    for(int v:a)
    {
        ans=max(ans,mp[v]+mp[v-1]);
    }
    cout << ans;

}


#define FILE "rollback"
int main()
{
        #ifdef ILDAR
            freopen("input.txt","r",stdin);
            freopen("output.txt","w",stdout);
        #endif // ILDAR



    //    freopen(FILE".in","r",stdin);
    //    freopen(FILE".out","w",stdout);
       if(!debug)
       {
            ios_base::sync_with_stdio(0);
            cin.tie(0);
            cout.tie(0);
       }

        int t=1;
   //     //scanf("%d",&t);
       // cin >> t;
         while(t--)
            solve();
        return 0;
}