read_line.to_i.times do
  a, b, c = read_line.split.map(&.to_i64)
  if c == 1
    puts -1
    next
  end
  dfs = Hash(Int64, Int64).new do |h, n|
    if n == 0
      h[n] = 0
    elsif n % c == 0
      h[n] = {h[n // c] + b, (n + c - 2)//(c - 1)*b}.min
    else
      h[n] = {h[n - n % c] + b, (n + c - 2)//(c - 1)*b}.min
    end
  end
  puts dfs[a]
end