Buggy python submission (verdict: Time Limit Exceeded):
n,m = map(int,input().split())
a = [input().rstrip() for i in range(n)]
b = list(zip(*a))
for i in range(m):
  b[i] = "".join(b[i])
ans = 0
ct1 = [[0 for k in range(n-j+1)] for j in range(n+1)]
ct2 = [[0 for k in range(n-j+1)] for j in range(n+1)]
for i in range(m-1):
  b1 = b[i]
  b2 = b[i+1]
  for j in range(n+1):
    ct1[j][0] = 0
    ct2[j][0] = 0
    for k in range(n-j):
      ct1[j][k+1] = ct1[j][k]
      ct2[j][k+1] = ct2[j][k]
      if b1[k+j] == b2[k]:
        ct1[j][k+1] += 1
      if b2[k+j] == b1[k]:
        ct2[j][k+1] += 1
  dp = [[10**6 for i in range(n+1)] for j in range(n+1)]
  dp[0][0] = 0
  for i in range(n+1):
    for j in range(n+1):
      if i <= j:
        cost = ct2[j-i][n-j]
      else:
        cost = ct1[i-j][n-i]
      if i < n:
        dp[i+1][j] = min(dp[i+1][j],dp[i][j]+cost)
      if j < n:
        dp[i][j+1] = min(dp[i][j+1],dp[i][j]+cost)
  ans += dp[-1][-1]
print(ans)

Fixed submission:
n,m = map(int,input().split())
a = [input().rstrip() for i in range(n)]
b = list(zip(*a))
for i in range(m):
  b[i] = "".join(b[i])
ans = 0
ct1 = [[0 for k in range(n-j+1)] for j in range(n+1)]
ct2 = [[0 for k in range(n-j+1)] for j in range(n+1)]
dp = [[10**5 for i in range(n+1)] for j in range(n+1)]
for i in range(m-1):
  b1 = b[i]
  b2 = b[i+1]
  for j in range(n+1):
    ct1[j][0] = 0
    ct2[j][0] = 0
    for k in range(n-j):
      ct1[j][k+1] = ct1[j][k]
      ct2[j][k+1] = ct2[j][k]
      if b1[k+j] == b2[k]:
        ct1[j][k+1] += 1
      if b2[k+j] == b1[k]:
        ct2[j][k+1] += 1
  dp[0][0] = 0
  for i in range(n+1):
    if i < n:
      dp[i+1][0] = 10**6
    for j in range(n+1):
      if i == 0 and j < n:
        dp[i][j+1] = 10**6
      if i <= j:
        cost = ct2[j-i][n-j]
      else:
        cost = ct1[i-j][n-i]
      if j < n:
        dp[i][j+1] = min(dp[i][j+1],dp[i][j]+cost)
      if i < n:
        dp[i+1][j] = dp[i][j]+cost
  ans += dp[-1][-1]
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
n,m = map(int,input().split())
a = [input().rstrip() for i in range(n)]
b = list(zip(*a))
for i in range(m):
  b[i] = "".join(b[i])
ans = 0
ct1 = [[0 for k in range(n-j+1)] for j in range(n+1)]
ct2 = [[0 for k in range(n-j+1)] for j in range(n+1)]
for i in range(m-1):
  b1 = b[i]
  b2 = b[i+1]
  for j in range(n+1):
    ct1[j][0] = 0
    ct2[j][0] = 0
    for k in range(n-j):
      ct1[j][k+1] = ct1[j][k]
      ct2[j][k+1] = ct2[j][k]
      if b1[k+j] == b2[k]:
        ct1[j][k+1] += 1
      if b2[k+j] == b1[k]:
        ct2[j][k+1] += 1
  dp = [[10**6 for i in range(n+1)] for j in range(n+1)]
  dp[0][0] = 0
  for i in range(n+1):
    for j in range(n+1):
      if i <= j:
        cost = ct2[j-i][n-j]
      else:
        cost = ct1[i-j][n-i]
      if i < n:
        dp[i+1][j] = min(dp[i+1][j],dp[i][j]+cost)
      if j < n:
        dp[i][j+1] = min(dp[i][j+1],dp[i][j]+cost)
  ans += dp[-1][-1]
print(ans)

Fixed submission:
n,m = map(int,input().split())
a = [input().rstrip() for i in range(n)]
b = list(zip(*a))
for i in range(m):
  b[i] = "".join(b[i])
ans = 0
ct1 = [[0 for k in range(n-j+1)] for j in range(n+1)]
ct2 = [[0 for k in range(n-j+1)] for j in range(n+1)]
dp = [[10**5 for i in range(n+1)] for j in range(n+1)]
for i in range(m-1):
  b1 = b[i]
  b2 = b[i+1]
  for j in range(n+1):
    ct1[j][0] = 0
    ct2[j][0] = 0
    for k in range(n-j):
      ct1[j][k+1] = ct1[j][k]
      ct2[j][k+1] = ct2[j][k]
      if b1[k+j] == b2[k]:
        ct1[j][k+1] += 1
      if b2[k+j] == b1[k]:
        ct2[j][k+1] += 1
  dp[0][0] = 0
  for i in range(n+1):
    if i < n:
      dp[i+1][0] = 10**6
    for j in range(n+1):
      if i == 0 and j < n:
        dp[i][j+1] = 10**6
      if i <= j:
        cost = ct2[j-i][n-j]
      else:
        cost = ct1[i-j][n-i]
      if j < n:
        dp[i][j+1] = min(dp[i][j+1],dp[i][j]+cost)
      if i < n:
        dp[i+1][j] = dp[i][j]+cost
  ans += dp[-1][-1]
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
n,m = map(int,input().split())
a = [input().rstrip() for i in range(n)]
b = list(zip(*a))
for i in range(m):
  b[i] = "".join(b[i])
ans = 0
for i in range(m-1):
  b1 = b[i]
  b2 = b[i+1]
  ct1 = [[0 for k in range(n-j+1)] for j in range(n+1)]
  ct2 = [[0 for k in range(n-j+1)] for j in range(n+1)]
  for j in range(n+1):
    for k in range(n-j):
      if b1[k+j] == b2[k]:
        ct1[j][k+1] += ct1[j][k]+1
      else:
        ct1[j][k+1] += ct1[j][k]
      if b2[k+j] == b1[k]:
        ct2[j][k+1] += ct2[j][k]+1
      else:
        ct2[j][k+1] += ct2[j][k]
  dp = [[10**6 for i in range(n+1)] for j in range(n+1)]
  dp[0][0] = 0
  for i in range(n+1):
    for j in range(n+1):
      if i <= j:
        cost = ct2[j-i][n-j]
      else:
        cost = ct1[i-j][n-i]
      if i < n:
        dp[i+1][j] = min(dp[i+1][j],dp[i][j]+cost)
      if j < n:
        dp[i][j+1] = min(dp[i][j+1],dp[i][j]+cost)
  ans += dp[-1][-1]
print(ans)

Fixed submission:
n,m = map(int,input().split())
a = [input().rstrip() for i in range(n)]
b = list(zip(*a))
for i in range(m):
  b[i] = "".join(b[i])
ans = 0
ct1 = [[0 for k in range(n-j+1)] for j in range(n+1)]
ct2 = [[0 for k in range(n-j+1)] for j in range(n+1)]
dp = [[10**5 for i in range(n+1)] for j in range(n+1)]
for i in range(m-1):
  b1 = b[i]
  b2 = b[i+1]
  for j in range(n+1):
    ct1[j][0] = 0
    ct2[j][0] = 0
    for k in range(n-j):
      ct1[j][k+1] = ct1[j][k]
      ct2[j][k+1] = ct2[j][k]
      if b1[k+j] == b2[k]:
        ct1[j][k+1] += 1
      if b2[k+j] == b1[k]:
        ct2[j][k+1] += 1
  dp[0][0] = 0
  for i in range(n+1):
    if i < n:
      dp[i+1][0] = 10**6
    for j in range(n+1):
      if i == 0 and j < n:
        dp[i][j+1] = 10**6
      if i <= j:
        cost = ct2[j-i][n-j]
      else:
        cost = ct1[i-j][n-i]
      if j < n:
        dp[i][j+1] = min(dp[i][j+1],dp[i][j]+cost)
      if i < n:
        dp[i+1][j] = dp[i][j]+cost
  ans += dp[-1][-1]
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
n,m = map(int,input().split())
a = [input() for i in range(n)]
b = list(zip(*a))
for i in range(m):
  b[i] = "".join(b[i])
ans = 0
for i in range(m-1):
  b1 = b[i]
  b2 = b[i+1]
  ct1 = [[0 for k in range(n-j+1)] for j in range(n+1)]
  for j in range(n+1):
    b2c = b2[:n-j]
    for k in range(n-j):
      if b1[k+j] == b2c[k]:
        ct1[j][k+1] += ct1[j][k]+1
      else:
        ct1[j][k+1] += ct1[j][k]
  ct2 = [[0 for k in range(n-j+1)] for j in range(n+1)]
  for j in range(n+1):
    b1c = b1[:n-j]
    for k in range(n-j):
      if b2[k+j] == b1c[k]:
        ct2[j][k+1] += ct2[j][k]+1
      else:
        ct2[j][k+1] += ct2[j][k]
  dp = [[10**6 for i in range(n+1)] for j in range(n+1)]
  dp[0][0] = 0
  for i in range(n+1):
    for j in range(n+1):
      if i <= j:
        cost = ct2[j-i][n-j]
      else:
        cost = ct1[i-j][n-i]
      if i < n:
        dp[i+1][j] = min(dp[i+1][j],dp[i][j]+cost)
      if j < n:
        dp[i][j+1] = min(dp[i][j+1],dp[i][j]+cost)
  ans += dp[-1][-1]
print(ans)

Fixed submission:
n,m = map(int,input().split())
a = [input().rstrip() for i in range(n)]
b = list(zip(*a))
for i in range(m):
  b[i] = "".join(b[i])
ans = 0
ct1 = [[0 for k in range(n-j+1)] for j in range(n+1)]
ct2 = [[0 for k in range(n-j+1)] for j in range(n+1)]
dp = [[10**5 for i in range(n+1)] for j in range(n+1)]
for i in range(m-1):
  b1 = b[i]
  b2 = b[i+1]
  for j in range(n+1):
    ct1[j][0] = 0
    ct2[j][0] = 0
    for k in range(n-j):
      ct1[j][k+1] = ct1[j][k]
      ct2[j][k+1] = ct2[j][k]
      if b1[k+j] == b2[k]:
        ct1[j][k+1] += 1
      if b2[k+j] == b1[k]:
        ct2[j][k+1] += 1
  dp[0][0] = 0
  for i in range(n+1):
    if i < n:
      dp[i+1][0] = 10**6
    for j in range(n+1):
      if i == 0 and j < n:
        dp[i][j+1] = 10**6
      if i <= j:
        cost = ct2[j-i][n-j]
      else:
        cost = ct1[i-j][n-i]
      if j < n:
        dp[i][j+1] = min(dp[i][j+1],dp[i][j]+cost)
      if i < n:
        dp[i+1][j] = dp[i][j]+cost
  ans += dp[-1][-1]
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
n,m = map(int,input().split())
a = [input() for i in range(n)]
b = list(zip(*a))
ans = 0
for i in range(m-1):
  b1 = b[i]
  b2 = b[i+1]
  ct1 = [[0 for k in range(n-j+1)] for j in range(n+1)]
  for j in range(n+1):
    b2c = b2[:n-j]
    for k in range(n-j):
      if b1[k+j] == b2c[k]:
        ct1[j][k+1] += ct1[j][k]+1
      else:
        ct1[j][k+1] += ct1[j][k]
  ct2 = [[0 for k in range(n-j+1)] for j in range(n+1)]
  for j in range(n+1):
    b1c = b1[:n-j]
    for k in range(n-j):
      if b2[k+j] == b1c[k]:
        ct2[j][k+1] += ct2[j][k]+1
      else:
        ct2[j][k+1] += ct2[j][k]
  dp = [[10**6 for i in range(n+1)] for j in range(n+1)]
  dp[0][0] = 0
  for i in range(n+1):
    for j in range(n+1):
      if i <= j:
        cost = ct2[j-i][n-j]
      else:
        cost = ct1[i-j][n-i]
      if i < n:
        dp[i+1][j] = min(dp[i+1][j],dp[i][j]+cost)
      if j < n:
        dp[i][j+1] = min(dp[i][j+1],dp[i][j]+cost)
  ans += dp[-1][-1]
print(ans)

Fixed submission:
n,m = map(int,input().split())
a = [input().rstrip() for i in range(n)]
b = list(zip(*a))
for i in range(m):
  b[i] = "".join(b[i])
ans = 0
ct1 = [[0 for k in range(n-j+1)] for j in range(n+1)]
ct2 = [[0 for k in range(n-j+1)] for j in range(n+1)]
dp = [[10**5 for i in range(n+1)] for j in range(n+1)]
for i in range(m-1):
  b1 = b[i]
  b2 = b[i+1]
  for j in range(n+1):
    ct1[j][0] = 0
    ct2[j][0] = 0
    for k in range(n-j):
      ct1[j][k+1] = ct1[j][k]
      ct2[j][k+1] = ct2[j][k]
      if b1[k+j] == b2[k]:
        ct1[j][k+1] += 1
      if b2[k+j] == b1[k]:
        ct2[j][k+1] += 1
  dp[0][0] = 0
  for i in range(n+1):
    if i < n:
      dp[i+1][0] = 10**6
    for j in range(n+1):
      if i == 0 and j < n:
        dp[i][j+1] = 10**6
      if i <= j:
        cost = ct2[j-i][n-j]
      else:
        cost = ct1[i-j][n-i]
      if j < n:
        dp[i][j+1] = min(dp[i][j+1],dp[i][j]+cost)
      if i < n:
        dp[i+1][j] = dp[i][j]+cost
  ans += dp[-1][-1]
print(ans)