#include<cstdio>
#include<iostream>
#include<algorithm>
using namespace std;

int n,k;
int h[20];
int ans;

int main(){
	#ifndef DEBUG
		string FileName="round";
		freopen((FileName+".in").c_str(),"r",stdin);
		freopen((FileName+".out").c_str(),"w",stdout);
	#endif
	scanf("%d%d",&n,&k);
	for(int i = 1; i <= n; i++)scanf("%d",&h[i]);
	do{
		int flag = 1;
		for(int i = 1; i <= n; i++){
			if(h[i]-h[i-1] > k){
				flag = 0;
				break;
			}
		}
		ans += flag;
	}while(next_permutation(h+1,h+n+1));
	printf("%d",ans/n);
}