public class FlourPacker {

    public static void main(String[] args) {
        System.out.println(getLargestPrime(217));
    }


    public static int getLargestPrime(int number) {
        int toReturn = 0;
        if (number <= 1) {
            return -1;
        } else {
            // checking if given number is the prime number
            boolean isPrime = false;
            int count = 0;
            for(int i = number; i > 0; i--) {
                if(number % i == 0) {
                    count++;
                    if(count > 2) {
                        isPrime = false;
                        break;
                    }
                    else if(count == 2) {
                        isPrime = true;
                    }
                }
            }
            if(isPrime) {
                toReturn = number;
            } else {
                int count2 = 0;
                for(int i = (number - 1); i > 0; i--) {
                    if(number % i == 0) {
                        // below checking if devider is the prime number
                        count2 = 0;
                        for(int x = i; x > 0; x--) {
                            if (i % x == 0) {
                                count2++;
                            }
                        }

                        if(count2 == 2) {
                            int multiplier = 1;
                            int toCompare = 0;
                            while(multiplier * i <= number)
                                if(multiplier * i == number) {
                                    toCompare = i;
                                    if(toCompare > toReturn) {
                                        toReturn = i;
                                        break;
                                    } else {
                                        break;
                                    }

                            } else {
                                    multiplier++;

                                }
                        }


                    }
                }



            }
        }
        return toReturn;
    }

}