#include<cstdio>
#include<cstdlib>
#include<algorithm>
#include<iostream>
#include<queue>
#include<vector>
#include <bitset>
#include <cmath>
#include <limits>
#include <iostream>
using namespace std;
#define INF 100000
#define MAX 100000
#define MOD 1000000007
typedef long long ll;
typedef pair<int,int> P;
typedef pair< pair<int,int>, int> p; 
#define bit(n,k) ((n>>k)&1) /*nのk bit目*/

//https://gist.github.com/FF256grhy/6424de0e315a242f19620c0019fba004


int main(){
    int Q;
    cin>>Q;
    for(int i=0;i<Q;i++){
        ll A,B,C;
        cin>>A>>B>>C;
        ll count=0;
        if(C==1){
            cout<<-1<<endl;
            continue;
        }
        while(A>2*C-2){
            count++;
            if(A%C==0){
                A/=C;
            }else A-=A%C;
        }
        if(A!=0){
            if(A<C) count++;
            else count+=2;
        }
        cout<<count*B<<endl;
    }
}