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 Go (1.6) (judge verdict: Accepted)

package main

import (
	"fmt"
	"math"
)

func main() {
	var x int
	fmt.Scan(&x)
	var answer int
	for a := x; ; a++ {
		if isPrime(a) {
			answer = a
			break
		}
	}
	fmt.Println(answer)
}

func isPrime(x int) bool {
	var upperBound int
	upperBound = int(math.Sqrt(float64(x)) + 1)
	for divider := 2; divider < upperBound; divider++ {
		if x%divider == 0 {
			return false
		}
	}
	return true
}