#include <bits/stdc++.h>
using namespace std;
using lint = long long;
template<class T = int> using V = vector<T>;
template<class T = int> using VV = V< V<T> >;

int main() {
  cin.tie(nullptr); ios::sync_with_stdio(false);
  int q; cin >> q;
  while (q--) {
    int a, b, c; cin >> a >> b >> c;
    if (c == 1) {
      cout << -1 << '\n';
      continue;
    }
    auto fn = [&](auto& F, int x) -> int {
      if (!x) return 0;
      if (x % c) {
        return min(F(F, x / c * c) + 1, (x + c - 2) / (c - 1));
      } else {
        return min(F(F, x / c) + 1, (x + c - 2) / (c - 1));
      }
    };
    cout << (lint)b * fn(fn, a) << '\n';
  }
}