<p>You are given a <strong>0-indexed</strong> 2D integer array <code>nums</code>. Initially, your score is <code>0</code>. Perform the following operations until the matrix becomes empty:</p> <ol> <li>From each row in the matrix, select the largest number and remove it. In the case of a tie, it does not matter which number is chosen.</li> <li>Identify the highest number amongst all those removed in step 1. Add that number to your <strong>score</strong>.</li> </ol> <p>Return <em>the final <strong>score</strong>.</em></p> <p> </p> <p><strong>Example 1:</strong></p> <pre> <strong>Input:</strong> nums = [[7,2,1],[6,4,2],[6,5,3],[3,2,1]] <strong>Output:</strong> 15 <strong>Explanation:</strong> In the first operation, we remove 7, 6, 6, and 3. We then add 7 to our score. Next, we remove 2, 4, 5, and 2. We add 5 to our score. Lastly, we remove 1, 2, 3, and 1. We add 3 to our score. Thus, our final score is 7 + 5 + 3 = 15. </pre> <p><strong>Example 2:</strong></p> <pre> <strong>Input:</strong> nums = [[1]] <strong>Output:</strong> 1 <strong>Explanation:</strong> We remove 1 and add it to the answer. We return 1.</pre> <p> </p> <p><strong>Constraints:</strong></p> <ul> <li><code>1 <= nums.length <= 300</code></li> <li><code>1 <= nums[i].length <= 500</code></li> <li><code>0 <= nums[i][j] <= 10<sup>3</sup></code></li> </ul>