#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("Yes");}else{puts("No");}
#define MAX_N 200005

int main() {
    int Q;
    cin >> Q;
    rep(loop, Q){
        ll a,b,c;
        cin >> a >> b >> c;
        ll ans = 0;
        if(c == 1){
            cout << "-1" << endl;
            continue;
        }
        while(a > 0){
            if(a < c){
                ans++;
                a = 0;
                continue;
            }
            if(a <= (c-1)*2){
                ans += 2;
                a = 0;
                continue;
            }
            if(a % c == 0){
                a /= c;
                ans++;
            }else{
                a -= a%c;
                ans++;
            }
        }

        cout << ans * b << endl;
    }
    
    return 0;
}