sub f {
#234567890#234567890#234567890#234567890#234567890#234567890#234567890#234567890
for(1..($b=pop)++){$b++;$b--if$_%4;$b++if$_%100;$b--if$_%400}$b%7
}

##</code><code>##

sub f {
#234567890#234567890#234567890#234567890#234567890#2
$b+=$_%400?$_%100?$_%4?0:1:0:1for 1..($b=pop)++;$b%7
}