#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define rrep(i,n) for(int i=(int)(n-1);i>=0;i--)
#define FOR(i,n,m) for(int i=n;i<=(int)(m);i++)
#define RFOR(i,n,m) for(int i=(int)(n);i>=m;i--)
#define all(x) (x).begin(),(x).end()
#define sz(x) int(x.size())
typedef long long ll;
const int INF = 1e9;
const int MOD = 1e9+7;
const ll LINF = 1e18;
const double PI=3.14159265358979323846;
using namespace std;
vector<int> dy={1,0,-1,0};
vector<int> dx={0,1,0,-1};
template<class T>
vector<T> make_vec(size_t a){
    return vector<T>(a);
}
template<class T, class... Ts>
auto make_vec(size_t a, Ts... ts){
    return vector<decltype(make_vec<T>(ts...))>(a, make_vec<T>(ts...));
}

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