import sys
input = sys.stdin.readline

T=int(input())
for tests in range(T):
    N,A,W,K=map(int,input().split())

    if K!=N:

        OK=-2
        NG=1<<60

        while NG-OK>1: # K-1人がOK+1点、一人がOK取れるか？
            mid=(OK+NG)//2

            if (mid+1)*(K-1)+mid<=A:
                OK=mid
            else:
                NG=mid

        if OK>=0:
            print(OK)
            continue

        if W>=N-K:
            print(-1)
            continue
        else:
            print(":(")
            continue

    ANS=A//N
    MINUS=(W+N-1)//N
    ANS-=MINUS*(MINUS+1)//2

    if A%N==N-1 or W%N==1:
        print(ANS)
    elif A>=N-1:
        print(ANS-1)
    elif W>=2:
        print(A//N-(MINUS+1)*(MINUS+2)//2)
    else:
        print(":(")