<p>The <strong>letter value</strong> of a letter is its position in the alphabet <strong>starting from 0</strong> (i.e. <code>'a' -> 0</code>, <code>'b' -> 1</code>, <code>'c' -> 2</code>, etc.).</p> <p>The <strong>numerical value</strong> of some string of lowercase English letters <code>s</code> is the <strong>concatenation</strong> of the <strong>letter values</strong> of each letter in <code>s</code>, which is then <strong>converted</strong> into an integer.</p> <ul> <li>For example, if <code>s = "acb"</code>, we concatenate each letter's letter value, resulting in <code>"021"</code>. After converting it, we get <code>21</code>.</li> </ul> <p>You are given three strings <code>firstWord</code>, <code>secondWord</code>, and <code>targetWord</code>, each consisting of lowercase English letters <code>'a'</code> through <code>'j'</code> <strong>inclusive</strong>.</p> <p>Return <code>true</code> <em>if the <strong>summation</strong> of the <strong>numerical values</strong> of </em><code>firstWord</code><em> and </em><code>secondWord</code><em> equals the <strong>numerical value</strong> of </em><code>targetWord</code><em>, or </em><code>false</code><em> otherwise.</em></p> <p> </p> <p><strong>Example 1:</strong></p> <pre> <strong>Input:</strong> firstWord = "acb", secondWord = "cba", targetWord = "cdb" <strong>Output:</strong> true <strong>Explanation:</strong> The numerical value of firstWord is "acb" -> "021" -> 21. The numerical value of secondWord is "cba" -> "210" -> 210. The numerical value of targetWord is "cdb" -> "231" -> 231. We return true because 21 + 210 == 231. </pre> <p><strong>Example 2:</strong></p> <pre> <strong>Input:</strong> firstWord = "aaa", secondWord = "a", targetWord = "aab" <strong>Output:</strong> false <strong>Explanation:</strong> The numerical value of firstWord is "aaa" -> "000" -> 0. The numerical value of secondWord is "a" -> "0" -> 0. The numerical value of targetWord is "aab" -> "001" -> 1. We return false because 0 + 0 != 1. </pre> <p><strong>Example 3:</strong></p> <pre> <strong>Input:</strong> firstWord = "aaa", secondWord = "a", targetWord = "aaaa" <strong>Output:</strong> true <strong>Explanation:</strong> The numerical value of firstWord is "aaa" -> "000" -> 0. The numerical value of secondWord is "a" -> "0" -> 0. The numerical value of targetWord is "aaaa" -> "0000" -> 0. We return true because 0 + 0 == 0. </pre> <p> </p> <p><strong>Constraints:</strong></p> <ul> <li><code>1 <= firstWord.length, </code><code>secondWord.length, </code><code>targetWord.length <= 8</code></li> <li><code>firstWord</code>, <code>secondWord</code>, and <code>targetWord</code> consist of lowercase English letters from <code>'a'</code> to <code>'j'</code> <strong>inclusive</strong>.</li> </ul>