sub A
{
    my ($m, $n) = @_;
    return 0    if $n == 0; 
    return 2*$n if $n >  0 and $m == 0;
    return 2    if $n == 1 and $m >  0;
    A($m-1, A($m, $n-1));
}

print A ($ARGV[0], $ARGV[1]), "\n";