<p>You are given 2 <strong>positive</strong> integers <code>l</code> and <code>r</code>. For any number <code>x</code>, all positive divisors of <code>x</code> <em>except</em> <code>x</code> are called the <strong>proper divisors</strong> of <code>x</code>.</p>

<p>A number is called <strong>special</strong> if it has exactly 2 <strong>proper divisors</strong>. For example:</p>

<ul>
	<li>The number 4 is <em>special</em> because it has proper divisors 1 and 2.</li>
	<li>The number 6 is <em>not special</em> because it has proper divisors 1, 2, and 3.</li>
</ul>

<p>Return the count of numbers in the range <code>[l, r]</code> that are <strong>not</strong> <strong>special</strong>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">l = 5, r = 7</span></p>

<p><strong>Output:</strong> <span class="example-io">3</span></p>

<p><strong>Explanation:</strong></p>

<p>There are no special numbers in the range <code>[5, 7]</code>.</p>
</div>

<p><strong class="example">Example 2:</strong></p>

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">l = 4, r = 16</span></p>

<p><strong>Output:</strong> <span class="example-io">11</span></p>

<p><strong>Explanation:</strong></p>

<p>The special numbers in the range <code>[4, 16]</code> are 4 and 9.</p>
</div>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= l &lt;= r &lt;= 10<sup>9</sup></code></li>
</ul>

class Solution:
    def nonSpecialCount(self, l: int, r: int) -> int:
        # 1 is not special, and any prime number is not special
        # only prime**2 is special, because if x=a*b, then it has at least 3 proper divisors (1,a,b)
        def isPrime(n):
            for d in range(2,int(n**0.5)+1):
                if n%d == 0:
                    return False
            return True
        
        a,b = int(l**0.5),int(r**0.5)
        if a**2<l or a==1:
            a += 1
        isPrime = [True]*(b+1)
        isPrime[0] = isPrime[1] = False
        for i in range(2,int(b*0.5)+1):
            if isPrime[i]:
                for j in range(i*i,len(isPrime),i):
                    isPrime[j] = False
        return r-l+1-sum(isPrime[a:b+1])
17200