Use the technique you learned in <A HREF=ex4_09.html>previous
exercise</A>, and re-design your
<A HREF=prime_sqrt.html>program which counts the number of primes</A>.
Compare the speed of this version with the one using sqrt().

<HR>
The program output is the same:
<PRE>
<CODE>
N = ? <B>100</B>

There are 25 prime numbers.
</CODE>
</PRE>

For N = 2000000, this version should be able to complete the calculation
within 0.5 second, while the one only applying the technique of sqrt() may take 5 seconds.