import std.stdio, std.array, std.conv;
 
void main(string[] args)
{
    try
    {
        auto source = args.length > 1 ? File(args[1], "r") : stdin;
        auto text   = source.byLine.join.to!(string);
 
        writeln(text);
    }
    catch (Exception ex)
    {
        writeln(ex.msg);
    }
}