#include <bits/stdc++.h>

using namespace std;

using ll = long long;

ll solve(ll a, ll b, ll c) {
    if (c == 1) return -1;

    vector<ll> v;
    ll aa = a;
    while (aa > 0) {
        v.push_back(aa % c);
        aa /= c;
    }
    reverse(v.begin(), v.end());

    int sz = v.size();
    ll ans = max(sz - 2, 0);
    for (int i = 1; i < sz; i += 2) {
        ll val = v[i - 1] * c + v[i];
        if (val == 0) continue;
        ans += (val <= 2 * (c - 1) ? 2 : 3);
    }
    ans *= b;
    return ans;
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int q;
    cin >> q;
    for (int i = 0; i < q; i++) {
        ll a, b, c;
        cin >> a >> b >> c;
        cout << solve(a, b, c) << "\n";
    }
    return 0;
}