#!/usr/bin/perl

# affine.pl

# usage, to transform the phrase "THE SECRET WORD IS PASTA" by the map x -> 3*x + 13:

# echo "THE SECRET WORD IS PASTA" | affine.pl 3 13


$a = $ARGV[0];
$b = $ARGV[1];

$plaintext = <STDIN>;

$plaintext =~ s/\s+//g;

@chars = split('',$plaintext);

for $c (@chars) {
    print chr(($a*(ord($c)-ord("A"))+$b)%26+ord("A"));
}

print "\n";