#! perl -wl
die unless defined ($dir=shift@ARGV);
for (</mit/ghc/src/package-patches/packages/$dir/*>){
    die unless m,/(\d\d).*\.patch$,;
    $used{$1}=1;
}
for($i=0;;++$i){
    $s=sprintf("%02d",$i);
    last unless $used{$s};
}
print$s;