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 C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Linq;

public class Program
{
    static void Main()
    {
        int x = int.Parse(Console.ReadLine());
        bool flag;
        while (true)
        {
            flag = true;
            for (int i = 2; i * i <= x; i++)
            {
                if (x % i == 0)
                {
                    flag = false;
                }
            }
            if (flag)
                break;
            else
                x++;
        }
        Console.WriteLine(x);
    }
}