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 Kotlin (1.0.0) (judge verdict: Accepted)

fun main(args: Array<String>) {
    val x = readLine()!!.toInt()
    val max = (1.5 * x).toInt()
    val list = Array<Boolean>(max + 1) { i -> true }
    for (i in (2..max).step(2)) {
        list[i] = false
    }

    for (i in (3..max).step(2)) {
        val v = list[i]
        if (v) {
            for (n in ((i + i)..max).step(i)) {
                list[n] = false
            }
        }
    }
    list[2] = true
    for (i in (x..max)) {
        if (list[i]) {
            println(i)
            return
        }
    }
}