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;

namespace ConsoleApp14
{
    class Program
    {
        static void Main(string[] args)
        {
            var solver = new Solver();
            solver.Calc();
        }
    }

    public class Solver
    {


        bool IsPrime(int x)
        {
            for (var i = 2; i < x; i++)
            {
                if (x % i == 0)
                {
                    return false;
                }

            }

            return true;

        }

        public void Calc()
        {

            var X = int.Parse(Console.ReadLine());

            while (true)
            {
                if (IsPrime(X))
                {
                    Console.WriteLine(X);
                    return;
                }
                else
                {
                    X++;
                }

            }


        }
    }
}