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

map<int,int>t;
map<int,int>num;
map<int,int>k;
int main()
{
	int ans=0;
	int n,m;
	cin>>n>>m;	
	int maxT=0;
	for(int i=1;i<=n;i++)cin>>t[i],maxT=max(maxT,t[i]);
	//int num[maxT+m]={0};
	for(int i=1;i<=n;i++) num[t[i]] ++ ,num[t[i]+m]--;
	//int k[maxT+m]={0};
	for(int i=1;i<=maxT+m-1;i++)
	{
		k[i] = k[i-1] +num[i];
		if(k[i]==1) ans++;		
	}
	
	int maxva = -INT_MAX ;
	
	int qz[maxT+m]={0};
	for(int i=1;i<=maxT+m-1;i++)
	{
		if(k[i] == 1) qz[i] = qz[i-1] - 1;
		else if(k[i] == 2) qz[i] = qz[i-1] + 1;
		else qz[i]=qz[i-1];
	}
	for(int i=1;i<=n;i++)
	{
		maxva = max(maxva,qz[t[i]+m-1]-qz[t[i]-1]);		
	}
	cout<<maxva + m + ans <<endl;
	
	return 0;
}