//it isn't too tough :)
#include<bits/stdc++.h>
#define ll long long int
#define loop(i,a,b) for(int (i)=(a);(i)<(b);(i)++)
#define bp 1000000007
#define sz(a) int((a).size())
#define pb push_back
#define mp make_pair
#define all(c) (c).begin(),(c).end()
#define F first
#define S second
using namespace std;
typedef vector<ll> vi;
typedef vector<vi> vvi;
typedef pair<ll,ll> ii;
ll n,x[200],v[200],val;
void solve(){
	cin>>n;
	loop(i,0,n)cin>>val,v[val]++;
	ll mx=0;
	loop(i,1,100)
        mx=max(mx,v[i] + v[i+1]);
    cout<<mx;

}
int main (){
    solve();
	return 0;
}