n = int(input())
for i in range(n):
    a,b,c = map(int,input().split())
    if c == 1:
        print(-1)
        continue
    x = 0
    y = 10 ** 100
    while a > 0:
        y = min(y, x + b * ((a + c - 2) // (c - 1)))
        if a % c == 0:
            a //= c
        else:
            a -= a % c
        x += b
    print(min(x, y))