#include <iostream>
using namespace std;
using ll = long long;
constexpr ll INF = 1LL << 60;
ll q, a, b, c;

int main() {
  cin >> q;
  while(q--) {
    cin >> a >> b >> c;
    if(c == 1) {
      cout << -1 << '\n';
      continue;
    }

    ll ans = INF, cnt = 0;
    while(a) {
      ans = min(ans, cnt + (a + c - 2) / (c - 1));
      if(a % c) a -= a % c;
      else a /= c;
      ++cnt;
    }
    cout << ans * b << '\n';
  }
  return 0;
}