#!/usr/bin/perl

use strict;
use warnings;

our %opts;
my $lookup;

for (@ARGV) {$opts{$1}=$2 if (/([ABC]{1})=(\d+\.?\d*)/)}
$lookup = join '', sort keys %opts;
die "I need two sides!\n" unless (length($lookup)==2);
my $lut = {
   'AB' => sub {return 'C='.sqrt($opts{A}**2+$opts{B}**2)},
   'AC' => sub {return 'B='.sqrt($opts{C}**2-$opts{A}**2)},
   'BC' => sub {return 'A='.sqrt($opts{C}**2-$opts{B}**2)},
};
print &{$lut->{$lookup}}, "\n";