This problem is an interactive problem.

Your program is expected to communicate with an interactor program
through the standard input/output. Your program must give a correct
response to the interactor in each step of the communication.
The C++ source code of an interactor program is provided as
interactor.cc and validate_domjudge.h.

Usage of the interactor program (let interactor be the executable file name):

  interactor <input data> <answer file> <feedback dir>

<input data> is the input file (*.in file in this directory).
<answer file> is the corresponding answer file to the input file (*.ans
in this directory).
<feedback dir> is a directory that the interactor uses.
The interactor's standard input/output must be connected to your
program's standard output/input, respectively.
If your program gives a correct response to the interactor in each step of
the communication, interactor exits with exit code 42, which is stored in
$? shell variable. Otherwise, it exits with another exit code.

Example:

If your program is "solve" and execute it with input 01.in,

> mkdir feedback
> mkfifo fifo
> ./solve < fifo | ./interactor 01.in 01.ans feedback > fifo
(no command should be executed between judge and echo)
> echo $?

Being displayed 42 by the command "echo $?", your program answered
correctly for input 01.in.

