<p>Roman numerals are represented by seven different symbols: <code>I</code>, <code>V</code>, <code>X</code>, <code>L</code>, <code>C</code>, <code>D</code> and <code>M</code>.</p> <pre> <strong>Symbol</strong> <strong>Value</strong> I 1 V 5 X 10 L 50 C 100 D 500 M 1000</pre> <p>For example, <code>2</code> is written as <code>II</code> in Roman numeral, just two one's added together. <code>12</code> is written as <code>XII</code>, which is simply <code>X + II</code>. The number <code>27</code> is written as <code>XXVII</code>, which is <code>XX + V + II</code>.</p> <p>Roman numerals are usually written largest to smallest from left to right. However, the numeral for four is not <code>IIII</code>. Instead, the number four is written as <code>IV</code>. Because the one is before the five we subtract it making four. The same principle applies to the number nine, which is written as <code>IX</code>. There are six instances where subtraction is used:</p> <ul> <li><code>I</code> can be placed before <code>V</code> (5) and <code>X</code> (10) to make 4 and 9. </li> <li><code>X</code> can be placed before <code>L</code> (50) and <code>C</code> (100) to make 40 and 90. </li> <li><code>C</code> can be placed before <code>D</code> (500) and <code>M</code> (1000) to make 400 and 900.</li> </ul> <p>Given an integer, convert it to a roman numeral.</p> <p> </p> <p><strong class="example">Example 1:</strong></p> <pre> <strong>Input:</strong> num = 3 <strong>Output:</strong> "III" <strong>Explanation:</strong> 3 is represented as 3 ones. </pre> <p><strong class="example">Example 2:</strong></p> <pre> <strong>Input:</strong> num = 58 <strong>Output:</strong> "LVIII" <strong>Explanation:</strong> L = 50, V = 5, III = 3. </pre> <p><strong class="example">Example 3:</strong></p> <pre> <strong>Input:</strong> num = 1994 <strong>Output:</strong> "MCMXCIV" <strong>Explanation:</strong> M = 1000, CM = 900, XC = 90 and IV = 4. </pre> <p> </p> <p><strong>Constraints:</strong></p> <ul> <li><code>1 <= num <= 3999</code></li> </ul>