#include <bits/stdc++.h> 
using namespace std;
#define pb push_back
#define fi first
#define se second
#define SZ(x) ((int)(x.size()))
#define FOI(i,a,n) for(int (i)=int(a);(i)<=int(n);++(i))
#define FOD(i,a,n) for(int (i)=int(a);(i)>=int(n);--(i))
#define IN(x,y) ((y).find((x))!=(y).end())
#define ALL(t) t.begin(),t.end()
#define MSET(tabl,i) memset(tabl, i, sizeof(tabl))
#define PSET(x,y) fixed<<setprecision(y)<<x

typedef long long ll;
typedef long double lf;
typedef pair<int, int> pi;
typedef vector<pi> vpi;
typedef vector<int> vi;

int toint(const string &s) { stringstream ss; ss << s; int x; ss >> x; return x; }
string tostring ( int number ){  stringstream ss; ss<< number; return ss.str();}

const int INF = 1e9;
const int NMAX=1;
const ll MOD = 1000000007;

int T,N,M;	
int a,b;
map<int, int> coun;

int main(){
	ios_base::sync_with_stdio(0);
	cin>>N;
	FOI(i,1,N){
		cin>>a;
		coun[a]++;
	}
	int ma = 0, mai = -1;
	FOI(i,1,99){
		if(!coun[i])
			continue;
		if(coun[i] + coun[i-1] >= ma){
			ma = coun[i] + coun[i-1];
		}
	}
	cout<<ma;
	return 0;
	
}