/* ****GT_18**** */

#include<bits/stdc++.h>
#define	MIN(a,b,c)	min(min(a,b),c)
#define	MAX(a,b,c)	max(max(a,b),c)
#define ll          long long
#define pb          push_back
#define mp          make_pair
#define pii         pair<int,int>
#define vi          vector<int>
#define all(a)      (a).begin(),(a).end()
#define F           first
#define S           second
#define sz(x)       (int)x.size()
#define hell        1000000007
#define endl        '\n'
#define rep(i,a,b)	for(int i=a;i<b;i++)
#define lbnd        lower_bound
#define ubnd        upper_bound
#define bs          binary_search
using namespace std;
int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	int t=1;
//	cin>>t;
	while(t--)
	{
		int n,ct=0;
		cin>>n;
		int b[101]={0};
		int a[n];
		rep(i,0,n){cin>>a[i];b[a[i]]++;}
		rep(i,0,100)
		{
			if(b[i]+b[i+1]>ct)
			ct=b[i]+b[i+1];
		}
		cout<<ct;
	}
	return 0;
}