Разделить матрицу на 4 части

import random
n = int(input("кол - во строк"))
m = int(input("кол - во столбцов"))
a = [[random.randrange(-10,10) for i in range(n)] for j in range(m)]
print("исходная матрица")
for i in range(n):
    for j in range(m):
        print("%4.0f" % a[j][i], end=' ')
    print()
l = int(input(" номер строки"))
k = int(input("номер столбца"))
for i in range(l - 1):
    for j in range(k - 1):
        print("%4.0f" % a[j][i], end=' ')
    print()
print()
for i in range(l, n):
    for j in range(k, m):
        print("%4.0f" % a[j][i], end=' ')
    print()
print()

def foo(matrix):
    l1 = len(matrix)//2
    l2 = len(matrix[0])//2
 
    print('----- I -----')
    for line in matrix[:l1]:
        print(line[:l2])
 
    print('----- II -----')
    for line in matrix[:l1]:
        print(line[l2:])
 
    print('----- III -----')
    for line in matrix[l1:]:
        print(line[:l2])
 
    print('----- IV -----')
    for line in matrix[l1:]:
        print(line[l2:])
 
 
matrix = [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12], [13, 14, 15, 16]]
for line in matrix:
    print(line)
foo(matrix)