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.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            uint X = uint.Parse(Console.ReadLine());
            bool flag;
            while (true)
            {
                flag = true;

                if(X == 2)
                {
                    break;
                }

                for (int i = 2; i <= X; i++)
                {
                    if(X == i)
                    {
                        break;
                    }

                    if(X % i == 0)
                    {
                        flag = false;
                        break;
                    }
                }

                if (flag) break;
                X++;
            }

            Console.WriteLine(X);

            return;
        }
    }
}