using System;

using System.Linq;

​

public class Program

{

    static bool isPrime(int n)

    {

 if (n <= 1) 

{

return false;

}

 if (n <= 3) 

{

return true;

 }

 if (n % 2 == 0 || n % 3 == 0)

{ 

return false;

} 

 for (int i = 5; i * i <= n; i = i + 6)

{

 if (n % i == 0 || n % (i + 2) == 0)

 return false;

 }

 return true;

 } 

    static int nextPrime(int N)

 {

 if (N <= 1)

{

 return 2;

 }

 int prime = N;

 bool found = false;

 while (!found)

 {

 prime++;

 if (isPrime(prime))

 found = true;

 }

 return prime;

 }

    public static void Main()

    {

        string val;

        int N;

        Console.WriteLine("Enter number:");

        val= Console.ReadLine();

        N = Convert.ToInt32(val);

        Console.WriteLine(nextPrime(N));

    }

​

​

}