Problem:
Score: 300 points

Problem Statement

Find the minimum prime number greater than or equal to X.

Notes

A prime number is an integer greater than 1 that cannot be evenly divided by any positive integer except 1 and itself.

For example, 2, 3, and 5 are prime numbers, while 4 and 6 are not.

Constraints

2 \le X \le 10^5

All values in input are integers.

Input

Input is given from Standard Input in the following format:

X

Output

Print the minimum prime number greater than or equal to X.

Sample Input 1

20

Sample Output 1

23

The minimum prime number greater than or equal to 20 is 23.

Sample Input 2

2

Sample Output 2

2

X itself can be a prime number.

Sample Input 3

99992

Sample Output 3

100003

Solution in Scala (2.11.7) (judge verdict: Accepted)

object Main {
  def main(args: Array[String]): Unit = {
    val num        = io.StdIn.readInt
    var prime_nums = Vector.empty[Int]

    (2 to num).foreach { i =>
      var flag = true
      (2 to Math.sqrt(i).toInt).foreach { j =>
        if(i%j == 0) flag = false
      }

      if(flag) prime_nums = prime_nums :+ i
    }
    
    var prime_flag = false
    var next_num = num

    if(prime_nums.last != num) {
      while(!prime_flag) {
        next_num += 1
        var flag = false
        prime_nums.foreach { i =>
          if(next_num%i == 0) flag = true
        }
        
        if(!flag) prime_flag = true
      }
    }

    println(next_num)
  }
}