read_line.to_i.times do
  n, m = read_line.split.map(&.to_i64)
  lo = 0i64
  hi = n + m + 1
  while hi - lo > 1
    mid = (lo + hi) // 2
    lack = {mid * 2 - m, 0}.max
    u = (lack + 3) // 4 * 2
    ok = (n - u) >= mid * 4
    if ok
      lo = mid
    else
      hi = mid
    end
  end
  puts lo * 3
end