Помогите с алгоритмом

    static int binarySearch(int[] A, int n) {
        int left = 0;
        int right = A.length;
        if (right == 0 || n > A[right - 1]) {
            return right;
        }

        while (left < right - 1) {
            int mid = (left + right) / 2;
            if (A[mid] <= n) {
                left = mid;
            } else {
                right = mid;
            }
        }
        return A[left] >= n ? left : right;
    }

    int leftIndex = binarySearch(A, left);
    int rightIndex = binarySearch(A, right + 1);
    int countBetweenLeftAndRight = rightIndex - leftIndex;