/*** author: yuji9511 ***/
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll,ll> lpair;
const ll MOD = 1e9+7;
const ll INF = 1e18;
#define rep(i,m,n) for(ll i=(m);i<(n);i++)
#define rrep(i,m,n) for(ll i=(m);i>=(n);i--)
#define printa(x,n) for(ll i=0;i<n;i++){cout<<(x[i])<<" \n"[i==n-1];};
void print() {}
template <class H,class... T>
void print(H&& h, T&&... t){cout<<h<<" \n"[sizeof...(t)==0];print(forward<T>(t)...);}
ll calc(ll A, ll C){
    ll amari = A % C;
    if(amari == A){
        return 1;
    }
    ll res = min(1 + calc((A-amari)/C, C) + (amari == 0 ? 0 : 1), (A + C-2) / (C-1));
    return res;

}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    ll Q;
    cin >> Q;
    while(Q--){
        ll A,B,C;
        cin >> A >> B >> C;
        if(C == 1){
            print(-1);
        }else{
            ll res = calc(A, C);
            print(res * B);

        }

    }
    

}