#include<bits/stdc++.h>
using namespace std;
using Int = long long;
template<typename T1,typename T2> inline void chmin(T1 &a,T2 b){if(a>b) a=b;}
template<typename T1,typename T2> inline void chmax(T1 &a,T2 b){if(a<b) a=b;}

//INSERT ABOVE HERE
signed main(){
  Int q;
  cin>>q;
  while(q--){
    Int a,b,c;
    cin>>a>>b>>c;
    if(c==1){
      cout<<-1<<endl;
      continue;
    }
    if(a<c){
      cout<<b<<endl;
      continue;
    }
    Int ans=a;
    for(Int i=0;i<31;i++){
      Int t=a,res=i;
      for(Int j=0;j<i;j++){
        if(t%c) res++;
        t/=c;
      }
      res+=(t+(c-2))/(c-1);
      chmin(ans,res);
    }
    cout<<ans*b<<endl;
  }
  return 0;
}