#include<bits/stdc++.h>
using namespace std;
#define f(i,a,b) for(ll i=a;i<b;i++)
#define fr(i,a,b) for(ll i=a;i>=b;i--)
#define ff(i,a,b,c) for(int i=a;i<b;i+=c)
#define w(n) while(n>0)
#define vi vector<int>
#define vll vector<long long int>
typedef pair<int,int> P;
typedef pair<pair<int,int> ,int> PII;
typedef pair<pair<long long int,long long int> ,long long int> PLL;
typedef pair<long long int,long long int> PL;
typedef long long int ll;
typedef long double ld;
typedef int I;
typedef string S;
ll gcd(ll n,ll m){if(m<=n && n%m==0)return m;if(n<m)return gcd(m,n);else return gcd(m,n%m);}
ll add(ll a,ll b,ll md){a=((a%md)+(b%md))%md;return a;}
ll sub(ll a,ll b,ll md){return add(a,md-b,md);}
ll bC(int n,int r){ll ans=1;if(r>n-r)r=n-r;f(i,1,r+1)ans=(ans*(n-i+1))/(i);return ans;}
ll mu(ll a,ll b,ll mod){return ((a%mod)*(b%mod))%mod; }
ll mul(ll a,ll b,ll mod){a%=mod;b%=mod;ld res=a;res*=b;ll c=(ll)(res/mod);a*=b;a-=c*mod;a%=mod;if(a<0)a+=mod;return a;}
ll mod_pow(ll a,ll b,ll mod){ll ans=1;while(b){if(b&1)ans=mul(ans,a,mod);a=mul(a,a,mod);b>>=1;}return ans;}
ll div(ll x,ll y,ll mod){return mul(x,mod_pow(y,mod-2,mod),mod);}
I main() {
    ll n ;
    cin >> n ;
    ll a[ n ] ;
    map< ll , ll > mp ;
    vector< ll > v ;
    ll ans = 0 ;
    f(i, 0, n ) {
        cin >> a[ i ] ;
        if( !mp.count( a[ i ] ) )
            v.push_back( a[ i ] ) ;
        mp[ a[ i ] ] ++;
        ans = max( ans ,mp[ a[ i ] ] ) ;
    }
    sort( v.begin() , v.end() ) ;
    f(i, 1, v.size() -1 ) {
        if( abs( v[ i ] - v[ i - 1 ] ) <= 1 ) {
            ans = max( ans , mp[ v[ i ] ] + mp[ v[ i -1 ] ] );
        }
    }
    cout << ans ;
}