#include <iostream>

using lint = long long;

void solve() {
    lint a, b, c;
    std::cin >> a >> b >> c;

    if (c == 1) {
        std::cout << -1 << std::endl;
        return;
    }

    lint ans = a, cost = 0;
    while (a > 0) {
        ans = std::min(ans, cost + (a + c - 2) / (c - 1));

        if (a % c != 0) ++cost;
        a -= a % c;
        ans = std::min(ans, cost + (a + c - 2) / (c - 1));

        ++cost;
        a /= c;
    }

    std::cout << ans * b << std::endl;
}

int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    int q;
    std::cin >> q;
    while (q--) solve();

    return 0;
}