#include<iostream>
#include<algorithm>
using namespace std;
int main()
{
	int n;
	cin>>n;
	int A[n],B[n];
	int i,j,k=0,l,flag1=1,flag2=1,m;
	for(i=0;i<n;i++)
	cin>>A[i];
	sort(A,A+n);
	int count=1,max=-1;
	for(i=0;i<n-1;i++)
	{
		for(j=i+1;j<n;j++)
		{
			if(A[j]-A[i]<=1)
			{
				count=count+1;
			}
		}
		if(count>max)
		max=count;
		count=1;		
	}
	if(max==1)
	max=0;
	cout<<max;
	return 0;
}