import java.io.*;
import java.lang.Math;

class Prime
{
    private static boolean isPrime(int p)
    {
        if (p < 2)
            return false;
        else {
            boolean prime = true;
            for (int a = 2; a < p; a++) {
                if ((p % a) == 0) {
                    prime = false;
                    break;
                }
            }
            return prime;
        }
    }

    public static void main(String[] args) throws IOException
    {
        BufferedReader input = 
            new BufferedReader(new InputStreamReader(System.in));

        int number = Integer.parseInt(input.readLine());

        if (isPrime(number))
            System.out.println("Entered integer " + number + " is prime.");
        else {
            int delta;

            if ((number % 2) != 0)
                delta = 2;
            else
                delta = 1;

            boolean found = false;
            do {
                if (isPrime(number - delta)) {
                    found = true;
                    int a = number - delta;
                    System.out.println(a);
                }

                if (isPrime(number + delta)) {
                    found = true;
                    System.out.println((new 
                        Integer(number + delta)).toString());
                }
                
                delta += 2;
            } while (!found);
        }
    }
}