#include <bits/stdc++.h>
using namespace std;
#define int long long
#define rep(i,n) for(int (i)=0;(i)<(n);(i)++)
#define rrep(i,n) for(int (i)=((n)-1);(i)>=0;(i)--)
#define itn int
#define all(x) (x).begin(),(x).end()
#define F first
#define S second
const long long INF = 1LL << 60;
const int MOD = 1000000007;
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }

int solve(int a,int b, int c){
    if(c == 1) return -1;
    int cnt = 0;
    while(a > (c-1)*2){
        if(a % c == 0) a/=c, cnt++;
        else {
            int res = a % c;
            cnt++;
            a -= res;
        }
    }
    while(a>0){
        a-= (c-1);
        cnt++;
    }

    return (cnt)*b;
}
signed main(void){
    int q; cin>>q;
    rep(i,q){
        int a,b,c; cin>>a>>b>>c;
        cout<<solve(a,b,c)<<endl;
    }
}