Buggy python submission (verdict: Runtime Error):
#D問題
N,C = map(int,input().split())
D = [list(map(int,input().split())) for i in range(C)]
c = [list(map(int,input().split())) for i in range(N)]
for i in range(N):
    for j in range(N):
        c[i][j]-=1
    

mod3 = [[0 for i in range(C)] for j in range(3)]
for i in range(N):
    for j in range(N):
        mod3[(i+j)%3][c[i][j]]+=1
        
c3 = [[0 for i in range(3)] for j in range(3)]
for i in range(3):
    for j in range(C):
        kari = 0
        for k in range(C):#kからjへ
            kari+=mod3[i][k]*D[k][j]
        c3[i][j] = kari
        
inf = float("inf")
MIN = inf

for i in range(C):
    C1 = c3[0][i]
    for j in range(C):
        if j != i:
            C2 = c3[1][j]
            for k in range(C):
                if k != i and k != j:
                    C3 = c3[2][k]
                    MIN = min(MIN,C1+C2+C3)
                    #print(C1,C2,C3)
                
if MIN != inf:
    print(MIN)
else:
    print(0)   


Fixed submission:
#D問題
N,C = map(int,input().split())
D = [list(map(int,input().split())) for i in range(C)]
c = [list(map(int,input().split())) for i in range(N)]
for i in range(N):
    for j in range(N):
        c[i][j]-=1
    

mod3 = [[0 for i in range(C)] for j in range(3)]
for i in range(N):
    for j in range(N):
        mod3[(i+j)%3][c[i][j]]+=1
        
c3 = [[0 for i in range(C)] for j in range(3)]
for i in range(3):
    for j in range(C):
        kari = 0
        for k in range(C):#kからjへ
            kari+=mod3[i][k]*D[k][j]
        c3[i][j] = kari
        
inf = float("inf")
MIN = inf

for i in range(C):
    C1 = c3[0][i]
    for j in range(C):
        if j != i:
            C2 = c3[1][j]
            for k in range(C):
                if k != i and k != j:
                    C3 = c3[2][k]
                    MIN = min(MIN,C1+C2+C3)
                    #print(C1,C2,C3)
                
if MIN != inf:
    print(MIN)
else:
    print(0)

Buggy python submission (verdict: Runtime Error):
#D問題
N,C = map(int,input().split())
D = [list(map(int,input().split())) for i in range(C)]
c = [list(map(int,input().split())) for i in range(N)]
for i in range(N):
    for j in range(N):
        c[i][j]-=1
    

mod3 = [[0 for i in range(C)] for j in range(3)]
for i in range(N):
    for j in range(N):
        mod3[(i+j)%3][c[i][j]]+=1
        
c3 = [[0 for i in range(3)] for j in range(3)]
for i in range(3):
    for j in range(C):
        kari = 0
        for k in range(C):#kからjへ
            kari+=mod3[i][k]*D[k][j]
        c3[i][j] = kari
        
inf = float("inf")
MIN = inf
for i in range(C):
    C1 = c3[0][i]
    for j in range(C):
        if j != i:
            C2 = c3[1][j]
            for k in range(C):
                if k != i and k != j:
                    C3 = c3[2][k]
                    MIN = min(MIN,C1+C2+C3)
                    #print(C1,C2,C3)

print(MIN)


Fixed submission:
#D問題
N,C = map(int,input().split())
D = [list(map(int,input().split())) for i in range(C)]
c = [list(map(int,input().split())) for i in range(N)]
for i in range(N):
    for j in range(N):
        c[i][j]-=1
    

mod3 = [[0 for i in range(C)] for j in range(3)]
for i in range(N):
    for j in range(N):
        mod3[(i+j)%3][c[i][j]]+=1
        
c3 = [[0 for i in range(C)] for j in range(3)]
for i in range(3):
    for j in range(C):
        kari = 0
        for k in range(C):#kからjへ
            kari+=mod3[i][k]*D[k][j]
        c3[i][j] = kari
        
inf = float("inf")
MIN = inf

for i in range(C):
    C1 = c3[0][i]
    for j in range(C):
        if j != i:
            C2 = c3[1][j]
            for k in range(C):
                if k != i and k != j:
                    C3 = c3[2][k]
                    MIN = min(MIN,C1+C2+C3)
                    #print(C1,C2,C3)
                
if MIN != inf:
    print(MIN)
else:
    print(0)