#include<bits/stdc++.h>
#define rep(I,K,N) for(ll (I) = (K) ; (I) < (N) ; (I) ++)
#define pb(x) push_back((x))
using namespace std;
typedef long long ll;

int main() {
     ios::sync_with_stdio(false);
 ll n;
 cin>>n;
 int arr[101];
 rep(i,-1,102)arr[i]=0;
 rep(i,0,n)
 {
     int x;
     cin>>x;
     arr[x]++;
 }
 int ans=0;
 rep(i,0,101)
 {
  ans=max(ans,max(arr[i]+arr[i-1],arr[i]+arr[i+1]));

 }
 cout<<ans<<endl;
    return 0;
}