#!/usr/bin/perl
while(1) {
	if (!$ARGV || /^IEA/)	{
		$/ = \1;
		1 while ($_ = <> || last) =~ /\s/;
		$/ = \104;
		die "Interchange can't start with $_" unless ($_ .= <>) =~ /^ISA[^\w\n]/;
		$/ = \(1 + y/\n//);
		$/ = substr( ($_ .= <>) , -1);
		die "Invalid terminator in $ARGV" if /\w$|\n.*\n$/ || ! s!\n|$/!!g;
	}
	else { last if !defined (($_ = <>) =~ s!\n|$/!!g); }
	print "$_\n";
}