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=head1 NAME

 gcd - compute greatest common divisor of two integers

=head1 SYNOPSIS

 gcd <a> <b>

=head1 DESCRIPTION

The B<gcd> program computes the greatest common divisor of two
arbitrary-precision integers I<a> and I<b>.  The result is written in
standard decimal notation to the standard output.

If I<b> is zero, B<gcd> will print an error message and exit.

=head1 SEE ALSO

invmod(1), isprime(1), lap(1)

=head1 AUTHOR

 Michael J. Fromberger <sting@linguist.dartmouth.edu>
 Thayer School of Engineering, Hanover, New Hampshire, USA