Buggy python submission (verdict: Time Limit Exceeded):
import itertools
import sys

N, N1 = tuple([int(x) for x in sys.stdin.readline().split()])
D, C = [], []

for _ in range(N1):
    D.append([int(x) for x in sys.stdin.readline().split()])
for _ in range(N):
    C.append([int(x) for x in sys.stdin.readline().split()])

color_count = [[0] * N1 for _ in range(3)]
for i in range(N):
    for j in range(N):
        color_count[(i + j) % 3][C[i][j] - 1] += 1

min_cost = 2**64
for colors in itertools.permutations(range(N1)):
    cost = 0
    for j in range(N1):
        cost += color_count[0][j] * D[j][colors[0]]
        cost += color_count[1][j] * D[j][colors[1]]
        cost += color_count[2][j] * D[j][colors[2]]
    if cost < min_cost:
        min_cost = cost
print(min_cost)

Fixed submission:
import itertools
import sys

N, N1 = tuple([int(x) for x in sys.stdin.readline().split()])
D, C = [], []

for _ in range(N1):
    D.append([int(x) for x in sys.stdin.readline().split()])
for _ in range(N):
    C.append([int(x) for x in sys.stdin.readline().split()])

color_count = [[0] * N1 for _ in range(3)]
for i in range(N):
    for j in range(N):
        color_count[(i + j) % 3][C[i][j] - 1] += 1

min_cost = 2**64
for c0 in range(N1):
    for c1 in range(N1):
        if c0 == c1:
            continue
        for c2 in range(N1):
            if c0 == c2 or c1 == c2:
                continue
            cost = 0
            for j in range(N1):
                cost += color_count[0][j] * D[j][c0]
                cost += color_count[1][j] * D[j][c1]
                cost += color_count[2][j] * D[j][c2]
            if cost < min_cost:
                min_cost = cost

print(min_cost)

Buggy python submission (verdict: Time Limit Exceeded):
import itertools
import sys

N, N1 = tuple([int(x) for x in sys.stdin.readline().split()])
D, C = [], []

for _ in range(N1):
    D.append([int(x) for x in sys.stdin.readline().split()])
for _ in range(N):
    C.append([int(x) for x in sys.stdin.readline().split()])

color_count = [[0] * N1 for _ in range(3)]
for i in range(N):
    for j in range(N):
        color_count[(i + j) % 3][C[i][j] - 1] += 1

min_cost = 2**64
for colors in list(itertools.permutations(range(N1))):
    cost = 0
    for i in range(3):
        for j, c in enumerate(color_count[i]):
            cost += c * D[j][colors[i]]
    if cost < min_cost:
        min_cost = cost
print(min_cost)

Fixed submission:
import itertools
import sys

N, N1 = tuple([int(x) for x in sys.stdin.readline().split()])
D, C = [], []

for _ in range(N1):
    D.append([int(x) for x in sys.stdin.readline().split()])
for _ in range(N):
    C.append([int(x) for x in sys.stdin.readline().split()])

color_count = [[0] * N1 for _ in range(3)]
for i in range(N):
    for j in range(N):
        color_count[(i + j) % 3][C[i][j] - 1] += 1

min_cost = 2**64
for c0 in range(N1):
    for c1 in range(N1):
        if c0 == c1:
            continue
        for c2 in range(N1):
            if c0 == c2 or c1 == c2:
                continue
            cost = 0
            for j in range(N1):
                cost += color_count[0][j] * D[j][c0]
                cost += color_count[1][j] * D[j][c1]
                cost += color_count[2][j] * D[j][c2]
            if cost < min_cost:
                min_cost = cost

print(min_cost)

Buggy python submission (verdict: Time Limit Exceeded):
import itertools
import sys

N, N1 = tuple([int(x) for x in sys.stdin.readline().split()])
D, C = [], []

for _ in range(N1):
    D.append([int(x) for x in sys.stdin.readline().split()])
for _ in range(N):
    C.append([int(x) for x in sys.stdin.readline().split()])

min_cost = 2**64
for colors in list(itertools.permutations(range(1, N1 + 1))):
    cost = 0
    for i in range(N):
        for j in range(N):
            if C[i][j] != colors[(i + j) % 3]:
                cost += D[C[i][j] - 1][colors[(i + j) % 3] - 1]
    if cost < min_cost:
        min_cost = cost
print(min_cost)

Fixed submission:
import itertools
import sys

N, N1 = tuple([int(x) for x in sys.stdin.readline().split()])
D, C = [], []

for _ in range(N1):
    D.append([int(x) for x in sys.stdin.readline().split()])
for _ in range(N):
    C.append([int(x) for x in sys.stdin.readline().split()])

color_count = [[0] * N1 for _ in range(3)]
for i in range(N):
    for j in range(N):
        color_count[(i + j) % 3][C[i][j] - 1] += 1

min_cost = 2**64
for c0 in range(N1):
    for c1 in range(N1):
        if c0 == c1:
            continue
        for c2 in range(N1):
            if c0 == c2 or c1 == c2:
                continue
            cost = 0
            for j in range(N1):
                cost += color_count[0][j] * D[j][c0]
                cost += color_count[1][j] * D[j][c1]
                cost += color_count[2][j] * D[j][c2]
            if cost < min_cost:
                min_cost = cost

print(min_cost)