import sys
input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#######################################################################
c = 0
n,m = na()
s = [list(input()) for i in range(n)]
a = s[0]
b = s[1]

for i in range(m):
    if a[i]!=b[i]:
        l = i
        break
for i in range(m-1,-1,-1):
    if a[i]!=b[i]:
        r = i
        break
x = a[:l]+[b[l]]+a[l:]
y = a[:r+1]+[b[r]]+b[r+1:]
ans = 1
for i in range(n):
    t = m+1
    for j in range(m):
        if s[i][j]!=x[j]:
            t = j
            break
    for j in range(t+1,m+1):
        if s[i][j-1]!=x[j]:
            ans = 0
if ans:
    c += 1
ans = 1
for i in range(n):
    t = m+1
    for j in range(m):
        if s[i][j]!=y[j]:
            t = j
            #print(i, j)
            break
    for j in range(t+1,m+1):
        if s[i][j-1]!=y[j]:
            ans = 0
            #print(i,t)
if ans:
    c += 1
print(c)