from sys import stdin

tt = int(stdin.readline())
ANS = []

for loop in range(tt):

    n,A,B = map(int,stdin.readline().split())
    a = list(map(int,stdin.readline().split()))
    a.sort()

    flag = True
    for i in range(2*n-1):
        if abs(a[i] - a[i+1]) > A:
            flag = False
            break
    if not flag:
        ANS.append(-1)
        continue

    acut = [ [] ]
    for i in range(2*n):
        if len(acut[-1]) == 0:
            acut[-1].append(a[i])
        elif abs( acut[-1][-1] - a[i] ) <= B:
            acut[-1].append(a[i])
        else:
            acut.append( [ a[i] ] )
    
    ans = 0
    wait = None

    for aci in range(len(acut)):

        nowlis = acut[aci]

        if wait == None:
            if len(nowlis) % 2 == 0:
                ans += len(nowlis)//2
            else:
                wait = nowlis[-1]
                ans += len(nowlis)//2
        else:
            if len(nowlis) % 2 == 1:
                ans += len(nowlis)//2
                wait = None
            else:
                # check next
                if ( aci==len(acut)-1  ): #next not exist
                    assert False #2n
                nexlis = acut[aci+1]
                if abs(wait-nexlis[0]) <= A: #pass ok
                    ans += len(nowlis)//2
                else: #pass ng
                    ans += len(nowlis)//2-1
                    wait = nowlis[-1]
    
    ANS.append(ans)

print (*ANS,sep="\n")