<?php

echo add ('109', '99')."\n";

function add ($x, $y) {
    $a = strlen ($x);
    $b = strlen ($y);
    $l = abs ($a - $b);
    $c = max ($a, $b) - 1;
    $u = 0;
    $r = '';

    if ($a > $b) $y = str_repeat ('0', $l) . $y;
    if ($b > $a) $x = str_repeat ('0', $l) . $x;
    while ($c != 0) {
        $d = $x[$c] + $y[$c] + $u;
        echo "$d\n" ;
        if ($d >= 10) {
            $r .= ($d % 10) + $u;
            $u = ($d / 10) % 10;
        } else {
            $r .= $d + $u;
            $u = 0;
        }

        $c--;
    }

    $r .= strrev ($x[0] + $y[0] + $u);
    return strrev ($r);
}