//
// Created by yamunaku on 2019/10/25.
//

#include <bits/stdc++.h>

using namespace std;

#define rep(i, n) for(int i = 0; i < (n); i++)
#define repl(i, l, r) for(int i = (l); i < (r); i++)
#define per(i, n) for(int i = ((n)-1); i >= 0; i--)
#define perl(i, l, r) for(int i = ((r)-1); i >= (l); i--)
#define all(x) (x).begin(),(x).end()
#define MOD9 998244353
#define MOD1 1000000007
#define IINF 1000000000
#define LINF 1000000000000000000
#define SP <<" "<<
#define CYES cout<<"Yes"<<endl
#define CNO cout<<"No"<<endl
#define CFS cin.tie(0);ios::sync_with_stdio(false)
#define CST(x) cout<<fixed<<setprecision(x)

typedef long long ll;
typedef long double ld;
typedef vector<int> vi;
typedef vector<vector<int>> mti;
typedef vector<ll> vl;
typedef vector<vector<ll>> mtl;

int main(){
    int q;
    cin >> q;
    rep(_, q){
        ll a, b, c;
        cin >> a >> b >> c;
        if(c == 1){
            cout << -1 << endl;
            continue;
        }
        ll sz = 1, tmp = 1;
        while(tmp < a) tmp *= c, sz++;
        mti cost(sz, vi(sz, 0));
        rep(i, sz){
            repl(j, i, sz){
                ll tmp = a, t1 = 1, t2 = 1;
                rep(k, sz - 1 - j) t1 *= c;
                rep(k, sz - i) t2 *= c;
                tmp /= t1;
                tmp %= (t2/t1);
                cost[i][j] = (tmp + c - 2) / (c - 1);
            }
        }
        vl dp(sz);
        rep(i, sz){
            dp[i] = cost[0][i] + (sz - 1 - i);
            rep(j, i){
                dp[i] = min(dp[i], dp[j] + cost[j + 1][i]);
            }
        }
        cout << dp[sz - 1] * b << endl;
    }
    return 0;
}