A - GPA計算　http://arc003.contest.atcoder.jp/tasks/arc003_1

gistfile1.pl

chomp($tani = <STDIN>);
chomp($hyouka = <STDIN>);
 
$hyouka =~ s/A/4/g;
$hyouka =~ s/B/3/g;
$hyouka =~ s/C/2/g;
$hyouka =~ s/D/1/g;
$hyouka =~ s/F/0/g;
 
@list = split //, $hyouka;
 
for (@list){
    $score = $score + $_;
}
 
 
$score = $score / $tani;
 
print $score,"\n";