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 Ruby (judge verdict: Accepted)

def is_prime?(num)
  if ! num.kind_of?(Integer) || num <= 1
    raise
  elsif [2, 3, 5, 7].include?(num)
    true
  elsif num.even?
    false
  else
    sqrt = (num**0.5).ceil
    flag = true
    3.step(sqrt, 2).each do |d|
      if num % d == 0
        flag = false
        break
      end
    end
    flag
  end
end

nums = readlines.map(&:to_i)
n = nums.shift
count = 0
nums.each do |num|
  count += 1 if is_prime?(num)
end
puts count