//--------------------------------------------------------\\
/////****//***********GABBAR STUDIOWORKS*************\\****\\\
//// /++++++++++++++++++++++++++++++\\1947 CUSTOMS\\\


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

typedef unsigned long long int ul;
typedef long long int ll;
typedef stack<int> stk;
typedef stack<char> stkc;
typedef stack<ll> stkl;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef pair <int,char> pr;
typedef priority_queue <int> pq;
typedef map<string,int>  msi;

#define FF first
#define SS second
#define pb push_back
#define pob pop_back
#define mp make_pair
#define mod 1000000007
#define INF 1e9
#define fi(i,k,n) for(int i=k;i<n;i++)
#define ful(i,k,n) for(ul i=k;i<n;i++)
#define frev(i,k,n) for(int i=n-1;i>=k;i--)
#define pb push_back
#define ln(s) s.length()
#define scns(s) getline(cin,s)
#define be(x) (x).begin(),(x).end()
#define setpr(x,y) cout<<fixed<<setprecision(y)<<x
#define intsct(s1,s2,s3) set_intersection(s1.begin(),s1.end(),s2.begin(),s2.end(),inserter(s3,s3.begin()));

int main()
{
    ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);    
    
    int n;
    cin>>n;

    map<int,int> count;

    for(int i=0;i<n;i++)
    {
        int temp;
        cin>>temp;
        count[temp]++;
    }

    int MAX = -1;

    for(int i=1;i<=99;i++)
    {
        if(count[i]==0)
            continue;

        int temp1 = count[i] + count[i-1];
        int temp2 = count[i] + count[i+1];

        int temp = max(temp1,temp2);

        MAX = max(MAX,temp);
    }

    cout<<MAX<<endl;
    return 0;
}