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)

import scala.io.{StdIn => in}

object Main extends App {

  val prime = Array.ofDim[Boolean](200001)
  for(i <- 2 to 200000) prime(i) = true

  for(i <- 2L to 200000L if prime(i.toInt)){
    for(j <- (i * i) to 200000L by i) {
      prime(j.toInt) = false 
    }
  }
  val x = in.readLine.toInt
  val ans = (x to 200000).filter(prime(_)).head
  println(ans)
}