Matrix-Search-Efficient

from typing import List

def find(X: List[List[int]], k: int):
    n = len(X)
    m = len(X[0])
    a = 0
    b = m - 1
    while a < n and b >= 0:
        if X[a][b] == k:
            break
        elif X[a][b] < k:
            a += 1
        else:
            b -= 1
    if a >= n or b < 0:
        return (-1, -1)  # not found
    return (a, b)