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;

namespace ConsoleApp3
{
	class Program
	{
		static void Main(string[] args)
		{
			int x = int.Parse(Console.ReadLine());
			for (int i = x; ; i++)
			{
				if (IsPrime(i))
				{
					Console.WriteLine(i);
					return;
				}
			}
		}

		static bool IsPrime(int num)
		{
			if (num == 1)
			{
				return true;
			}
			for (int i = 2; i * i <= num; i++)
			{
				if (num %i == 0)
				{
					return false;
				}
			}
			return true;
		}
	}
}