import java.io.*;
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < n; i++) {
            int a = sc.nextInt();
            long b = sc.nextInt();
            int c = sc.nextInt();
            if (c == 1) {
                sb.append("-1\n");
                continue;
            }
            int count = Integer.MAX_VALUE;
            int current = 0;
            while (a > 0) {
                count = Math.min(count, (a + c - 2) / (c - 1) + current);
                if (a % c == 0) {
                    a /= c;
                    current++;
                } else {
                    a -= a % c;
                    current++;
                }
            }
            count = Math.min(count, current);
            sb.append(count * b).append("\n");
        }
        System.out.print(sb);
    }
}
class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public String next() throws Exception {
        if (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
}