BLACK LINE

This is an **interactive problem**. It means that every time you output something, you must finish with a newline character and flush the output. For example, in C++ use the $fflush(stdout)$ function, in Java — call $System.out.flush()$, in Python — $sys.stdout.flush()$, and in Pascal — $flush(output)$. Only after flushing the output will you be able to read from the input again. There exists a s