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 isPrime(n int) bool {
	var tmp float64 = float64(n)
	rng := int(math.Ceil(math.Sqrt(tmp)))
	// fmt.Printf("rng = %d, n = %d, jajaja = %f\n", rng, n, math.Sqrt(float64(n)))
	for i := 2; i < rng; i++ {
		if n%i == 0 {
			return false
		}
	}
	return true
}

func main() {
	var x int
	fmt.Scan(&x)
	for i := x; i < 100004; i++ {
		if isPrime(i) {
			fmt.Println(i)
			break
		}
	}
}