def countLE(matrix, x):
    n = len(matrix)
    i, j = n - 1, 0
    cnt = 0
    while i >= 0 and j < n:
        if matrix[i][j] <= x:
            cnt += i + 1
            j += 1
        else:
            i -= 1
    return cnt

def kthSmallest(matrix, k):
    n = len(matrix)
    lo = matrix[0][0]
    hi = matrix[n-1][n-1]

    while lo < hi:
        mid = lo + (hi - lo) // 2
        if countLE(matrix, mid) >= k:
            ________
        else:
            ________
    return lo