#include<cstdio>

#include<algorithm>

#include<cmath>

using namespace std;

const int maxn = 21;

int height[30], pos[30];

long long dp[1 << maxn][21];

int main()

{

    int n, delta;

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

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

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

    for(int i = 1;i <= n; ++i) dp[pos[i]][i] = 1;

    for(int i = 1;i < pos[n + 1]; ++i)

    {

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

        {

            if((i & pos[j]) == 0) continue;

            int mx = i ^ pos[j];

            if(mx == 0) continue;

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

            {

                if( (i & pos[k]) == 0 || k == j || abs(height[j] - height[k]) <= delta) continue;

                dp[i][j] += dp[mx][k];

            }

        }

    }

    long long fin = 0;

    for(int i = 1;i <= n; ++i) fin += dp[pos[n + 1] - 1][i];

    printf("%lld",fin);

    return 0;

}