#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define pb push_back
#define fi first
#define se second
typedef pair<ll,ll> P;
using VP = vector<P>; using VVP = vector<VP>;
using VI = vector<ll>; using VVI = vector<VI>; using VVVI = vector<VVI>;
const int inf=1e9+7;
const ll INF=1LL<<60;
const ll Mod=998244353;

void solve(ll a,ll b,ll c){
  ll cnt=0;
  if(c==1) {
    cout<<-1<<endl;
    return;
  }
  while(a>=2*c-1){
    if(a%c!=0){
      a=a/c;
      cnt+=2;
    }
    else{
      a=a/c;
      cnt++;
    }
  }
  if(a==0) cnt+=0;
  else if(a<=c-1) cnt++;
  else cnt+=2;
  cout<<b*cnt<<endl;
}

int main(){
  int i,j;
  int q;
  cin>>q;
  for(int l=0;l<q;l++){
    ll a,b,c;
    cin>>a>>b>>c;
    solve(a,b,c);
  }
}