Kth element in Matrix

class Solution {
    public int kthSmallest(int[][] matrix, int k) {
        int n = matrix.length;
        int low = matrix[0][0];
        int high = matrix[n - 1][n - 1];

        while (low < high) {
            int mid = low + (high - low) / 2;
            int count = countLessEqual(matrix, mid);

            if (count < k)
                low = mid + 1;
            else
                high = mid;
        }

        return low;
    }

    private int countLessEqual(int[][] matrix, int target) {
        int n = matrix.length;
        int count = 0;

        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                if (matrix[i][j] <= target)
                    count++;
            }
        }

        return count;
    }
}