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 extends App {
  val x = readLine.toInt
  
  def check(n:Int): Int = {
    val sqrt = math.sqrt(n).toInt
    val notPrime = (2 +: (3 to sqrt).filter(_ % 2 == 1)).exists(n % _ == 0)
    if (n == 2) n
    else if (notPrime) check(n+1)
    else n
  }
  
  println(check(x))
}