Q = int(input())
for i in range(Q):
    A, B, C = map(int, input().split())
    if C == 1:
        print(-1)
        continue
    cnt = 0
    while True:
        if A < 2*C:
            A -= C-1
            cnt += 1
        else:
            A, b = A//C, A%C
            if b > 0:
                cnt += 1
            if A > 0:
                cnt += 1
        if A <= 0:
            break
    print(B*cnt)