#include <bits/stdc++.h>
using namespace std;

#define MOD 1000000007
#define pb push_back
#define mp make_pair
#define all(c) (c).begin(),(c).end()
#define sz(a) int((a).size())
#define F first
#define S second

#define rep(i, a, b) for(int i = a; i < b; ++i)
#define per(i, a, b) for(int i = a; i >= b; --i)
#define travel(c,itr) for(__typeof((c).begin()) itr=(c).begin();itr!=(c).end();itr++)
#define INDEX(arr,ind)			(lower_bound(all(arr),ind)-arr.begin())

#define scan(x) do{while((x=getchar())<'0'); for(x-='0'; '0'<=(_=getchar()); x=(x<<3)+(x<<1)+_-'0');}while(0)
char _;


typedef long long ll;
typedef long double ld;
typedef vector<int> vi;
typedef pair<int,int> pii;
typedef pair<ll,int> pli;
typedef pair<ll,ll> pll;
typedef pair<int, pii> piii;
typedef pair<ll, pll> plll;
typedef vector<pii> vpii;
typedef vector<piii> vpiii;

inline ll powmod(ll x, ll n, ll _mod){ 
  ll res = 1; 
  while (n){
    if (n & 1)res = (res*x) % _mod; 
    x = (x*x) % _mod; 
    n >>= 1;
    }
    return res; 
  }

// y = upper_bound(x) finds y > x

/*
//seive of erasthones
int p[1000006];
vi primes;

void gen(){
	memset(p,1,sizeof p);
	for(int i=2;i<1000006;i++){
		if(p[i]==0)continue;
		for(int j=2;i*j<1000006;j++){
			p[i*j]=1;
		}
	}
	for(int  i=2;i<1000006;i++){
		if(p[i]){
			primes.pb(i);
		}
	}
	//for(int i=0;i<10;i++)cout<<primes[i]<<endl;
}

*/

// The Great Captain Jack Sparrow //
#define N 100005
int n;
int a[200];
int c[200];

int main(){
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

// freopen("in.txt","r",stdin);
// freopen("o.txt","w",stdout);

cin>>n;
rep(i,0,n){
	cin>>a[i];
	c[a[i]]++;
}
int ans=1;
rep(i,0,120){
	if(c[i]){
		ans=max(ans,c[i]+c[i-1]);
		ans=max(ans,c[i]+c[i+1]);
	}
}
cout<<ans<<'\n';
return 0;
}