#include <cstdio>

#include <algorithm>

#define ll long long

#define setIO(s) freopen(s".in","r",stdin)

using namespace std;

int s[20];

ll dp[1<<18][17],fac[20];

int main() {

	// setIO("input");

	int n,k,i,j,l;

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

	fac[0]=1;

	for(i=1;i<=n;++i) fac[i]=fac[i-1]*i;

	for(i=0;i<n;++i) scanf("%d",&s[i]), dp[(1<<i)][i]=1;

    for(l=1;l<(1<<n);++l) {

    	for(j=0;(1<<j)<=l;++j) {

    		if((l&(1<<j)) && dp[l][j]) {

    			for(int p=0;(1<<p)<(1<<n);++p) {

    				if(((1<<p)^l)&&abs(s[p]-s[j])>k){

    					dp[l^(1<<p)][p]+=dp[l][j];

    				}

    			}

    		}

    	}

    }

    ll re=0;

    for(i=0;i<n;++i) re+=dp[(1<<n)-1][i];

    printf("%lld\n",re);

	return 0;

}