#include <bits/stdc++.h>
using namespace std;

#define int long long

signed main(){
  int q;cin>>q;
  while(q--){
    int a,b,c;cin>>a>>b>>c;
    if(c==1){
      cout<<-1<<endl;
      continue;
    }
    int ans=0;
    while(a){
      if(a<c){ans++;break;}
      if(a>c&&a<=2*(c-1)){ans+=2;break;}
      if(a%c)ans++;
      a/=c;ans++;
    }
    cout<<ans*b<<endl;
  }
}