#include<bits/stdc++.h>
using namespace std;const int N=2e6;vector<int>v[N+7];
int n,m,ans;
int main(){
	scanf("%d%d",&n,&m);
	for(int i=1,x;i<=n;++i)scanf("%d",&x),v[x+N/2].push_back(i);
	for(int i=0;i<=N;++i){
		if(i-m<0||i-m>N)continue;
		int n1=v[i].size(),n2=v[i-m].size(),i1=0,i2=0,s=0,mins=0,maxx=0;
		ans=max(ans,n1);
		if(!n1||!n2||m==0)continue;
		for(int j=0;j<n1+n2;++j){
			int t;
			if(i1!=n1&&(i2==n2||v[i][i1]<v[i-m][i2]))i1++,t=-1;
			else i2++,t=1;
			s+=t;maxx=max(maxx,s-mins);mins=min(mins,s);
		}
		ans=max(ans,maxx+n1);
	}
	printf("%d\n",ans);
	return 0;
}