Something

import java.math.BigInteger;
import java.util.Scanner;
public class FindPrime{
    public static void main(String [] args){
        Scanner in = new Scanner(System.in);
        BigInteger N = new BigInteger(in.next());
        BigInteger cnt = BigInteger.ONE;
        BigInteger res = N;
        boolean found = false;
        while (!found){
            BigInteger cand1 = N.add(cnt);
            BigInteger cand2 = N.subtract(cnt);
            if (cand1.isProbablePrime(200)){
                res = cand1;
                found = true;
                
            } else if (cand2.isProbablePrime(200)){
                res = cand2;
                found = true;
            }
            cnt = cnt.add(BigInteger.ONE);
        }
        System.out.format("Nearest prime found is %s\n",res.toString());
    }
}