#include <bits/stdc++.h>
#define si(n) scanf("%d",&n);
#define pi(n) printf("%d\n",n);
#define pl(n) printf("%lld\n",n);
#define sl(n) scanf("%lld",&n);
#define pd(n) printf("%lf\n",n);
#define ss(s) scanf("%s",s);
#define ps(s) printf("%s\n",s);
#define pb push_back
#define ll long long int
#define maxn 105
#define sqrtn 317
#define maxm 100005
#define minv(a,b,c) min(a,min(b,c))
#define pii pair<int,int>
#define pll pair<ll,ll>
#define eps 1e-9
#define mod 1000000007
#define psi pair < string,ll>
#define mp make_pair
using namespace std;
int arr[maxn];

int main()
{
	int n;
	si(n);
	int num;
	for(int i=0;i<n;i++)
	{
		si(num);
		arr[num]++;
	}
	int ans=0;
	for(int i=1;i<=100;i++)
	{
		ans=max(ans,arr[i]+arr[i-1]);
	}
	pi(ans);

}