#include "bits/stdc++.h"
#define REP(i, n) for(int i = 0; i < int(n); i++)
#define FOR(i,n,m) for(int i = int(n); i < int(m); i++)
using namespace std;
typedef long long ll;
const int MOD = 1e9 + 7;
const int INF = 1e9 + 6;
const ll LLINF = 1e18 + 1;

ll a, b, c;

ll solve(ll n = a) {
    if (n == 0) return 0;
    ll res = (n + c - 2) / (c - 1);
    res = min(res, solve(n / c) + 1 + (n % c == 0 ? 0 : 1));
    return res;
}

int main() {
    int q; cin >> q;
    REP(i, q) {
        cin >> a >> b >> c;
        if (c == 1) puts("-1");
        else {
            cout << solve() * b << endl;
        }
    }
    return 0;
}