/*input
6
4 6 5 3 3 1
*/
#include <bits/stdc++.h>
using namespace std;
#define ll long long
//loops
#define f(i,s,n) for(ll i=(ll)s;i<(ll)n;i++)
#define rf(i,n,s) for(ll i=(ll)(n-1);i>=(ll)s;i--)
//reset
#define ms0(X) memset((X), 0, sizeof((X)))
#define ms1(X) memset((X), -1, sizeof((X)))
//IO
#define bio ios_base::sync_with_stdio;cin.tie(NULL)
//STL
#define pb push_back
#define pii pair<ll,ll>
#define vll vector<ll>
#define vpii vector<pii >
#define mll map<ll, ll>
#define mpii map<pii,ll> 
#define msll map<string, ll> 
#define sortv(v) sort(v.begin(),v.end())
#define F first
#define S second
//standard values
#define mod (ll)(1e9+7)
#define INF (ll)1e16
#define MAXN (ll)(1e5+5)
//comparator
bool cmp(pii a,pii b){
  if(a.F==b.F) return a.S<b.S;
  else return a.F<b.F;
}
ll exp(ll a, ll b){ll ans=1;while(b!=0){if(b%2)ans=ans*a;a=a*a;b/=2;}return ans;}
/********************************************************************************************************/
ll has[105];
int main() 
{
  bio;
  ll n;
  cin>>n;
  f(i,0,n){
    ll a;
    cin>>a;
    has[a]++;
  }
  ll ans=0;
  f(i,0,100){
    ans=max(ans,has[i]+has[i+1]);
  }
  cout<<ans<<endl;
  return 0;
}