#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;
int main() {
	int Q;
	cin >> Q;
	while (Q--) {
		int A, B, C;
		cin >> A >> B >> C;
		if (C == 1) {
			cout << -1 << endl;
		}
		else {
			int ops = (A + C - 2) / (C - 1);
			vector<int> seq = { A };
			do {
				int x = seq.back();
				seq.back() %= C;
				seq.push_back(x / C);
				int cost = int(seq.size()) - 1;
				for (int i : seq) {
					cost += (i + C - 2) / (C - 1);
				}
				ops = min(ops, cost);
			} while (C != 1 && seq.back() >= C);
			cout << 1LL * ops * B << endl;
		}
	}
	return 0;
}