Buggy python submission (verdict: Time Limit Exceeded):
N,C=[int(x) for x in str(input()).split()]
D=[[0 for x in range(0,C+1)]]
for i in range (0,C):
  D.append([0]+[int(x) for x in str(input()).split()])
c=[[0 for x in range(0,N+1)]]
for j in range(0,N):
  c.append([0]+[int(x) for x in str(input()).split()])


error=1000000000
for i in range(1,C+1):
  for j in range(1,C+1):
    if j!=i:
      for k in range(1,C+1):
        if k!=j:
          if k!=i:
            
            e=0
            for x in range(1,N+1):
              for y in range(1,N+1):
                
                if (x+y)%3==0:
                  e+=D[c[x][y]][i]
                elif (x+y)%3==1:
                  e+=D[c[x][y]][j]
                elif (x+y)%3==2:
                  e+=D[c[x][y]][k]
                if e>error:
                  break
       
            error=min(error,e)
print(error)





Fixed submission:
N,C=[int(x) for x in str(input()).split()]
D=[[0 for x in range(0,C+1)]]
for i in range (0,C):
  D.append([0]+[int(x) for x in str(input()).split()])
c=[[0 for x in range(0,N+1)]]
for j in range(0,N):
  c.append([0]+[int(x) for x in str(input()).split()])



mod1=[0 for x in range(0,C+1)]
mod2=[0 for x in range(0,C+1)]
mod0=[0 for x in range(0,C+1)]

for x in range (1,N+1):
  for y in range(1,N+1):
    if (x+y)%3==0:
      mod0[c[x][y]]+=1
    elif (x+y)%3==1:
      mod1[c[x][y]]+=1
    else:
      mod2[c[x][y]]+=1



error=1000000000
for i in range(1,C+1):
  for j in range(1,C+1):
    if j!=i:
      for k in range(1,C+1):
        if k!=j:
          if k!=i:
            e=0

            for x in range(1,C+1):
              e+=mod0[x]*D[x][i]+mod1[x]*D[x][j]+mod2[x]*D[x][k]


       
            error=min(error,e)
print(error)

Buggy python submission (verdict: Time Limit Exceeded):
N,C=[int(x) for x in str(input()).split()]
D=[[0 for x in range(0,C+1)]]
for i in range (0,C):
  D.append([0]+[int(x) for x in str(input()).split()])
c=[[0 for x in range(0,N+1)]]
for j in range(0,N):
  c.append([0]+[int(x) for x in str(input()).split()])


error=1000000000
for i in range(1,C+1):
  for j in range(1,C+1):
    if j!=i:
      for k in range(1,C+1):
        if k!=j:
          if k!=i:
            
            e=0
            for x in range(1,N+1):
              for y in range(1,N+1):
                
                if (x+y)%3==0:
                
                  e+=D[c[x][y]][i]
                elif (x+y)%3==1:
              
                  e+=D[c[x][y]][j]
                elif (x+y)%3==2:
              
                  e+=D[c[x][y]][k]
                
       
            error=min(error,e)
print(error)





Fixed submission:
N,C=[int(x) for x in str(input()).split()]
D=[[0 for x in range(0,C+1)]]
for i in range (0,C):
  D.append([0]+[int(x) for x in str(input()).split()])
c=[[0 for x in range(0,N+1)]]
for j in range(0,N):
  c.append([0]+[int(x) for x in str(input()).split()])



mod1=[0 for x in range(0,C+1)]
mod2=[0 for x in range(0,C+1)]
mod0=[0 for x in range(0,C+1)]

for x in range (1,N+1):
  for y in range(1,N+1):
    if (x+y)%3==0:
      mod0[c[x][y]]+=1
    elif (x+y)%3==1:
      mod1[c[x][y]]+=1
    else:
      mod2[c[x][y]]+=1



error=1000000000
for i in range(1,C+1):
  for j in range(1,C+1):
    if j!=i:
      for k in range(1,C+1):
        if k!=j:
          if k!=i:
            e=0

            for x in range(1,C+1):
              e+=mod0[x]*D[x][i]+mod1[x]*D[x][j]+mod2[x]*D[x][k]


       
            error=min(error,e)
print(error)