#!/usr/bin/env perl

use strict;
use warnings;

use CGI ();
use JSON ();

my $q     = CGI->new;
my $json  = JSON->new->utf8;
my $input = $json->decode( $q->param('POSTDATA') );

my $a = $input->{a};
my $b = $input->{b};
my $c = $a + $b;

print $q->header("application/json");
print $json->encode({ c => $c });