#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> P;
#define DUMP(x) cout << #x << " = " << (x) << endl;
#define FOR(i, m, n) for (ll i = m; i < n; i++)
#define IFOR(i, m, n) for (ll i = n - 1; i >= m; i--)
#define REP(i, n) FOR(i, 0, n)
#define IREP(i, n) IFOR(i, 0, n)
#define FOREACH(x, a) for (auto&(x) : (a))
#define ALL(v) (v).begin(), (v).end()
#define SZ(x) ll(x.size())

void solve() {
  ll a, b, c;
  cin >> a >> b >> c;
  if (c == 1) {
    cout << -1 << endl;
    return;
  }
  ll cnt = 0;
  while (a > 0) {
    if (a % c == 0 || a < c)
      a /= c;
    else if (a - (c - 1) < c)
      a -= c - 1;
    else
      a -= a % c;
    cnt++;
  }

  cout << (ll)cnt * b << endl;
}

int main() {
  ll Q;
  cin >> Q;
  while (Q--) solve();
}