import sys
input = lambda: sys.stdin.readline().rstrip()

#  -----------------------  #

n, m = map(int, input().split())
S = [input() for _ in range(n)]
ans = 0
s = S[0]
t = S[1]
j = -1
for i in range(m):
  if s[i] != t[i]:
    j = i
    break
T1 = s[:j] + s[j] + t[j:]
T2 = s[:j] + t[j] + s[j:]

def isok(T, s):
  i = 0
  j = 0
  diff = 0
  while i < m and j < m+1:
    if s[i] != T[j]:
      diff += 1
      if diff == 2:
        break
      i -= 1
    i += 1
    j += 1
  else:
    return True
  return False

# T1?
for s in S:
  if not isok(T1, s):
    break
else:
  ans += 1
  
# T2?
for s in S:
  if not isok(T2, s):
    break
else:
  ans += 1
  
print(ans)