import numpy as np

a = np.array([
    [9, 3, 5],
    [2, 0, 3],
    [0, 1, -6],
])
b = np.array([
    [1, -1, -1],
    [-1, 4, 7],
    [8, 1, -1],
])
print(a, b, sep='\n')
print()

print(np.dot(a, b))
print()

N = 3
c = np.zeros((N, N))
for i in range(N):
    for j in range(N):
        c[i, j] = sum(a[i, k] * b[k, j] for k in range(N))

print(c)