Buggy python submission (verdict: Time Limit Exceeded):
n, c = map(int, input().split())
D = [tuple(map(int, input().split())) for _ in range(c)]
C = [tuple(map(lambda x:int(x)-1, input().split())) for _ in range(n)]

# 全ての色について違和感を記録
dst = [[0, 0, 0] for _ in range(c)]
for ci in range(c):
    for i in range(n):
        for j in range(n):
            c_from = C[i][j]
            dst[ci][(i+j)%3] += D[c_from][ci]

from itertools import permutations
d = 1000*500*500
for p0, p1, p2 in permutations(list(range(c)), 3):
    d = min(d, dst[p0][0] + dst[p1][1] + dst[p2][2])
print(d)


Fixed submission:
n, c = map(int, input().split())
D = [tuple(map(int, input().split())) for _ in range(c)]
C = [tuple(map(lambda x:int(x)-1, input().split())) for _ in range(n)]

# 全ての色について違和感を記録
dst = [[0, 0, 0] for _ in range(c)]
for ci in range(c):
    for i in range(n):
        for j in range(n):
            c_from = C[i][j]
            dst[ci][(i+j)%3] += D[c_from][ci]

from itertools import permutations
d = 1000*500*500
for p0, p1, p2 in permutations(list(range(c)), 3):
    d = min(d, dst[p0][0] + dst[p1][1] + dst[p2][2])
print(d)

Buggy python submission (verdict: Time Limit Exceeded):
n, c = map(int, input().split())
D = [tuple(map(int, input().split())) for _ in range(c)]
C = [tuple(map(lambda x:int(x)-1, input().split())) for _ in range(n)]

grid = [[(i+j)% 3 for i in range(n)] for j in range(n)]

# 全ての色について違和感を記録
dst = [[0, 0, 0] for _ in range(c)]
for ci in range(c):
    for i in range(n):
        for j in range(n):
            c_from = C[i][j]
            dst[ci][grid[i][j]] += D[c_from][ci]

from itertools import permutations
d = 1000*500*500
for p0, p1, p2 in permutations(list(range(c)), 3):
    d = min(d, dst[p0][0] + dst[p1][1] + dst[p2][2])
print(d)


Fixed submission:
n, c = map(int, input().split())
D = [tuple(map(int, input().split())) for _ in range(c)]
C = [tuple(map(lambda x:int(x)-1, input().split())) for _ in range(n)]

# 全ての色について違和感を記録
dst = [[0, 0, 0] for _ in range(c)]
for ci in range(c):
    for i in range(n):
        for j in range(n):
            c_from = C[i][j]
            dst[ci][(i+j)%3] += D[c_from][ci]

from itertools import permutations
d = 1000*500*500
for p0, p1, p2 in permutations(list(range(c)), 3):
    d = min(d, dst[p0][0] + dst[p1][1] + dst[p2][2])
print(d)

Buggy python submission (verdict: Time Limit Exceeded):
n, c = map(int, input().split())
D = [tuple(map(int, input().split())) for _ in range(c)]
C = [tuple(map(lambda x:int(x)-1, input().split())) for _ in range(n)]

grid = [[(i+j)% 3 for i in range(n)] for j in range(n)]

mind = 1000*500*500
from itertools import permutations
for p in permutations(list(range(c)), 3):
    sumd = 0
    for i in range(n):
        for j in range(n):
            c_to = p[grid[i][j]]
            c_from = C[i][j]
            sumd += D[c_from][c_to]
        if sumd > mind:
            break
    else:
        mind = sumd

print(mind)


Fixed submission:
n, c = map(int, input().split())
D = [tuple(map(int, input().split())) for _ in range(c)]
C = [tuple(map(lambda x:int(x)-1, input().split())) for _ in range(n)]

# 全ての色について違和感を記録
dst = [[0, 0, 0] for _ in range(c)]
for ci in range(c):
    for i in range(n):
        for j in range(n):
            c_from = C[i][j]
            dst[ci][(i+j)%3] += D[c_from][ci]

from itertools import permutations
d = 1000*500*500
for p0, p1, p2 in permutations(list(range(c)), 3):
    d = min(d, dst[p0][0] + dst[p1][1] + dst[p2][2])
print(d)