//let's keep it simple and easy....
#include<bits/stdc++.h>
#define ll          long long int
#define pb          emplace_back
#define mp          make_pair
#define pii         pair<int,int>
#define vi          vector<int>
#define Max(a,b)    ((a)>(b)?(a):(b))
#define Min(a,b)    ((a)<(b)?(a):(b))
#define rep(i,a,b)  for (__typeof((b)) i=(a);i<(b);i+=1)
#define all(a)      (a).begin(),(a).end()
#define F           first
#define S           second
#define sz(x)       (int)x.size()
#define mod	        1000000007
#define endl        '\n'
#define si(x)		scanf("%d",&x);
using namespace std;

int main()
{
	int n;
	cin >>n;
	int a[n];
	int b[100]={0};
	rep(i,0,n)
	{
		cin >>a[i];
		b[a[i]]+=1;
	}
	int max=0;
	rep(i,0,99)
	{
		//cout<<b[i]<<endl;
		if(max<b[i]+b[i+1])
		{
			max=b[i]+b[i+1];
		}
	}
	cout<<max;

}