1 #include <iostream>
2 #include <algorithm>
3 #include <cstring>
4 #include <cstdio>
5 #include <queue>
6 #define ll long long
7
8 using namespace std;
9 const int N = 1e5+1000;
10
11 int a[N],dp[N];
12
13 void solve()
14 {
15 int n,k;
16 scanf("%d %d",&n,&k);
17 for(int i = 0; i < n; i++)
18 {
19 scanf("%d",&a[i]);
20 }
21 sort(a,a+n);
22 memset(dp,0,sizeof(dp));
23 for(int i = n-1; i >= 0; i--)
24 {
25 dp[i] = 0x3f3f3f;
26 int j = upper_bound(a,a+n,a[i]+2*k)-a;
27 if(j - i >= 3) dp[i] = min(dp[j]+1,dp[i]);
28 if(j - i >= 4) dp[i] = min(dp[j-1]+1,dp[i]);
29 if(j - i >= 5) dp[i] = min(dp[j-2]+1,dp[i]);
30 }
31 if(dp[0] == 0x3f3f3f)
32 printf("-1\n");
33 else
34 printf("%d\n",dp[0]);
35 }
36
37 int main(void)
38 {
39 int t,cnt = 0;
40 scanf("%d",&t);
41
42 while(t--)
43 {
44 printf("Case %d: ",++cnt);
45 solve();
46 }
47 return 0;
48 }
