Description：

Solution：

Code：

#include<algorithm>

#include<iostream>

#include<cstdlib>

#include<cstdio>

#include<cmath>

#include<cstring>

using namespace std;

int n,k;

#define MAXN 17

int s[MAXN];

unsigned long long f[MAXN][1 << MAXN];

int main()

{

	scanf("%d%d",&n,&k);

	for(int i = 1;i <= n;++i)scanf("%d",&s[i]);

	int tot = (1 << n) - 1;

	for(int i = 1;i <= n;++i)f[i][1 << (i - 1)] = 1ll;

	for(int b = 1;b <= tot;++b)

	{

		for(int i = 1;i <= n;++i)

		{

			if(b & (1 << (i - 1)))

			{

				for(int j = 1;j <= n;++j)

				{

					if(!(b & (1 << (j - 1))))

					{

						if(abs(s[j] - s[i]) > k)

						{

							f[j][b | (1 << (j - 1))] += f[i][b];

						}

					}

				}

			}

		}

	}

	unsigned long long ans = 0;

	for(int i = 1;i <= n;++i)

	{

		ans += f[i][tot];

	}

	cout << ans << endl;

	return 0;

}