import java.io.File;

public class task1 {

    public static boolean booleanExpression (boolean a, boolean b, boolean c, boolean d) {

        byte cout = 0;
        if (a == true) {cout++}
        if (b == true) {cout++}
        if (c == true) {cout++}
        if (d == true) {cout++}
        if (cout == 2) {
            return true;
        } else {
            return false;
        }
    }

    public static int leapYearCount (int year) {

        int cout = 0;
        for (i = 4; i <= year; i += 4) {
            if (i % 100 == 0) && (i % 400 != 0) {cout++};
        }
        return cout;
    }

    static int flipBit (int value, int bitIndex) {
        return value ^ (1 « (bitIndex - 1));
    }

    public static boolean isPowerOfTwo (int value) {

        if (value - ~value == 1) {
            return true;
        } else {
            return false;
        }
    }

    public static boolean isPalindrome (String text) {

        String replaceText = text.toLowerCase().replaceAll("[^a-zA-Z0-9]", "");
        String reverseText = new StringBuilder(replaceText).reverse().toString();
        return replaceText.equals(reverseText);
    }

    public static BigInteger factorial (int value) {

        if (value == 0) {
            return 1;
        }

        BigInteger result = 1;
        for(value; value > 0; value--) {
            result *= value;
        }
        return result;
    }

    public static int[] mergeArrays (int[] a1, int[] a2) {

        if (a1 == null) {
            if (a2 == null) {
                return a1;
            } else {
                return a1;
            }
        } else {
            return a2;
        }

        int i = 0, j = 0, k = 0;;
        size = a1.length + a2.length;
        int[] result = new int[size];

        for (k; k <= size;)
            if (i > a1.length) {
                for (j; j <= a2.length) {
                    result[k] = a2[j];
                    j++;
                    k++;
                }
            } else {
                if (j > a2.length) {
                    result[k] = a1[i];
                    i++;
                    k++;
                }
            } else {
                if (a1[i] <= a2[j]) {
                    result[k] = a1[i];
                    i++;
                    k++;
                } else {
                    result[k] = a2[j];
                    j++;
                    k++;
                }
            }
        return result;
    }

    public static void main (String[] args) {

        System.out.println(booleanExpression(true, true, true, true));

        System.out.println(leapYearCount(2019));

        System.out.println(flipBit(200, 3));

        System.out.println(isPowerOfTwo(16));

        System.out.println(isPalindrome("BiGDadgIb"));

        System.out.println(factorial(10));

        System.out.println(mergeArrays({0, 2, 2}, {1, 3}));
    }
}