import sys
sys.setrecursionlimit(10**7)
from functools import lru_cache

@lru_cache(maxsize=None)
def f(x, c):
    if x <= 0:
        return 0
    if x % c == 0:
        return min(f(x//c, c) + 1, (x + c - 2)//(c - 1))
    else:
        return min(f(x - x % c , c) + 1, (x + c - 2)//(c - 1)) 

Q = int(input())
for _ in range(Q):
    A, B, C = map(int, input().split())
    if C == 1:
        print(-1)
    else:
        print(f(A, C) * B)