readlnOrNull function
Reads a line of input from the standard input stream and returns it,
or return null if EOF has already been reached when readlnOrNull is called.
Implementation
String? readlnOrNull() => readline();
Reads a line of input from the standard input stream and returns it,
or return null if EOF has already been reached when readlnOrNull is called.
String? readlnOrNull() => readline();