public static int diagonalDifference(List<List<Integer>> arr) {
        // Write your code here
        int primaryDiagonal = 0;
        int secondaryDiagonal = 0;
        int size = arr.size();
        for (int i = 0; i < size; i++) {
            for (int j = 0; j < size; j++) {
                if (i == j) {
                    primaryDiagonal += arr.get(i).get(j);
                    if (i == size - 1 - j) {
                        secondaryDiagonal += arr.get(i).get(j);
                    }
                } else if (i == size - 1 - j) {
                    secondaryDiagonal += arr.get(i).get(j);
                }
            }
        }

        return Math.abs(primaryDiagonal - secondaryDiagonal);
    }

    static String timeConversion(String s) {
        String hour = s.substring(0, 2);
        String marker = s.substring(s.length() - 2, s.length());
        if (marker.equals("PM") && !hour.equals("12")) {
            int temp = Integer.parseInt(hour) + 12;
            hour = temp + "";
        } else if (marker.equals("AM") && hour.equals("12")) {
            hour = "00";
        }
        String answer = hour + s.substring(2, s.length() - 2);
        return answer;
    }

    static String kangaroo(int x1, int v1, int x2, int v2) {
        int n = 0;
        int biggerGap = v1 > v2 ? v1 : v2;
        while (true) {
            int l1 = x1 + v1 * n;
            int l2 = x2 + v2 * n;
            if (l1 == l2) {
                return "YES";
            }
            if (l2 > l1 && v2 >= v1 || l1 > l2 && v1 >= v2) {
                return "NO";
            }
            n++;
        }
    }

    static int saveThePrisoner(int n, int m, int s) {
        int answer = m + s - 1;
        if (answer > n) {
            answer = answer % n;
        }

        return answer == 0 ? n : answer;
    }