Find cyclic number

import java.math.BigInteger;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner cin = new Scanner(System.in);
        int n = cin.nextInt();
        int x = cin.nextInt();
        int b = x - 1;
        if (n == 1) {
            System.out.print(b);
            return;
        }
        while (b > 1) {
            if (checkCyclic(b, n + 1) == true) {
                System.out.print(b);
                return;
            }
            b--;
        }
        System.out.print(-1);
    }

    private static boolean checkCyclic(int b, int p) {
        if (checkBdivP(b, p) == true) {
            return false;
        }
        if (checkPrime(p) == false) {
            return false;
        }
        BigInteger bBig = new BigInteger(String.valueOf(b), 10);
        BigInteger soMu = bBig;
        for (int i = 2; i <= p-1; i++) {
            soMu = soMu.multiply(bBig);
        }
        BigInteger pBig = new BigInteger(String.valueOf(p), 10);
        BigInteger motBig = new BigInteger("1", 10);
        BigInteger soMuTru1 = soMu.subtract(motBig);
        BigInteger koBig = new BigInteger("0", 10);
        if (soMuTru1.mod(pBig).equals(koBig) == true) {
            System.out.println(soMuTru1.divide(pBig));
        }
        return soMuTru1.mod(pBig).equals(koBig);
    }

    private static boolean checkPrime(int number) {
        if (number < 2) {
            return false;
        }
        if (number == 2 || number == 3) {
            return true;
        }
        for (int i = 2; i < number; i++) {
            if (number % i == 0) {
                return false;
            }
        }
        return true;
    }

    private static boolean checkBdivP(int b, int p) {
        return b % p == 0;
    }

}