#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <queue>
#include <string>
#include <map>
#include <set>
#include <stack>
#include <tuple>
#include <deque>
#include <array>
#include <numeric>
#include <bitset>
#include <iomanip>
#include <cassert>
#include <chrono>
#include <random>
#include <limits>
#include <iterator>
#include <functional>
#include <sstream>
#include <fstream>
#include <complex>
#include <cstring>
#include <unordered_map>
using namespace std;

using ll = long long;
using P = pair<int, int>;
constexpr int INF = 1001001001;
constexpr int mod = 1000000007;
// constexpr int mod = 998244353;

template<class T>
inline bool chmax(T& x, T y){
    if(x < y){
        x = y;
        return true;
    }
    return false;
}
template<class T>
inline bool chmin(T& x, T y){
    if(x > y){
        x = y;
        return true;
    }
    return false;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int Q;
    cin >> Q;
    for(int q = 0; q < Q; ++q){
        ll A, B, C;
        cin >> A >> B >> C;
        if(C == 1){
            cout << -1 << '\n';
            continue;
        }
        if(A < C){
            cout << B << '\n';
            continue;
        }

        // coeff[k] := A を C 進表記したときの k 次の係数
        vector<ll> coeff;
        while(A > 0){
            coeff.emplace_back(A % C);
            A /= C;
        }
        int n = coeff.size();
        
        ll ans = 0;
        if(coeff[n - 1] * C + coeff[n - 2] <= C * 2 - 2){
            ans += (coeff[n - 1] * C + coeff[n - 2] + C - 2) / (C - 1) * B;
        }
        else{
            ans += ((coeff[n - 1] > 0) + (coeff[n - 2] > 0) + 1) * B;
        }
        for(int k = n - 3; k >= 0; --k){
            // C 倍による左ビットシフト
            ans += B;
            // [1, C) を足すことで係数を調整
            if(coeff[k] > 0)    ans += B;
        }

        cout << ans << '\n';
    }

    return 0;
}