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"content": "<p>You are given a string <code>s</code> of length <code>n</code> where <code>s[i]</code> is either:</p>\n\n<ul>\n\t<li><code>'D'</code> means decreasing, or</li>\n\t<li><code>'I'</code> means increasing.</li>\n</ul>\n\n<p>A permutation <code>perm</code> of <code>n + 1</code> integers of all the integers in the range <code>[0, n]</code> is called a <strong>valid permutation</strong> if for all valid <code>i</code>:</p>\n\n<ul>\n\t<li>If <code>s[i] == 'D'</code>, then <code>perm[i] > perm[i + 1]</code>, and</li>\n\t<li>If <code>s[i] == 'I'</code>, then <code>perm[i] < perm[i + 1]</code>.</li>\n</ul>\n\n<p>Return <em>the number of <strong>valid permutations</strong> </em><code>perm</code>. Since the answer may be large, return it <strong>modulo</strong> <code>10<sup>9</sup> + 7</code>.</p>\n\n<p> </p>\n<p><strong>Example 1:</strong></p>\n\n<pre>\n<strong>Input:</strong> s = "DID"\n<strong>Output:</strong> 5\n<strong>Explanation:</strong> The 5 valid permutations of (0, 1, 2, 3) are:\n(1, 0, 3, 2)\n(2, 0, 3, 1)\n(2, 1, 3, 0)\n(3, 0, 2, 1)\n(3, 1, 2, 0)\n</pre>\n\n<p><strong>Example 2:</strong></p>\n\n<pre>\n<strong>Input:</strong> s = "D"\n<strong>Output:</strong> 1\n</pre>\n\n<p> </p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>n == s.length</code></li>\n\t<li><code>1 <= n <= 200</code></li>\n\t<li><code>s[i]</code> is either <code>'I'</code> or <code>'D'</code>.</li>\n</ul>\n",
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