Problem:
Prime Numbers

A prime number is a natural number which has exactly two distinct natural number divisors: 1 and itself. For example, the first four prime numbers are: 2, 3, 5 and 7.

Write a program which reads a list of N integers and prints the number of prime numbers in the list.

Input

The first line contains an integer N, the number of elements in the list.

N numbers are given in the following lines.

Output

Print the number of prime numbers in the given list.

Constraints

1 ≤ N ≤ 10000

2 ≤ an element of the list ≤ 108

Sample Input 1

5
2
3
4
5
6

Sample Output 1

3

Sample Input 2

11
7
8
9
10
11
12
13
14
15
16
17

Sample Output 2

4

Solution in PHP (judge verdict: Accepted)

<?php

class CalculateSum {

    public function getAnswer()
    {
        $n = trim(fgets(STDIN));
        $count = 0;

        for ($i = 0; $i < $n; $i++) {
            $num = (int) fgets(STDIN);

            if ($this->isPrime($num)) {
                $count++;
            }
        }

        echo $count . PHP_EOL;
    }
}

class CheckPrimeNumbers extends CalculateSum {

    public function isPrime($num)
    {
        if ($num == 2) {
            return true;
        } elseif ( $num < 2 or $num % 2 == 0) {
            return false;
        } else {
            $start = 3;
            while ($start <= sqrt($num)) {
                if ($num % $start == 0) {
                    return false;
                }
                $start += 2;
            }
            return true;
        }
    }
}

$rate = new CheckPrimeNumbers();
$rate->getAnswer();