import sys
import pypyjit

pypyjit.set_param('max_unroll_recursion=-1')

sys.setrecursionlimit(200005)
int1 = lambda x: int(x)-1
pDB = lambda *x: print(*x, end="\n", file=sys.stderr)
p2D = lambda x: print(*x, sep="\n", end="\n\n", file=sys.stderr)
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def SI(): return sys.stdin.readline().rstrip()
dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
# dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
inf = (1 << 63)-1
# inf = (1 << 31)-1
md = 10**9+7
# md = 998244353

def compare(s, t):
    l = r = 0
    pre = []
    for i in range(m):
        pre.append(s[i])
        if s[i] != t[i]:
            l = i+1
            break
    pos = []
    for i in range(m)[::-1]:
        pos.append(t[i])
        if s[i] != t[i]:
            r=i+1
            break
    for i in range(l,r):pre.append(s[i])
    return pre+pos[::-1]

def check(t):
    if not t: return False
    for s in ss:
        if ng(s, t): return False
    return True

def ng(s, t):
    t = iter(t)
    for c in s:
        if c not in t: return True
    return False

def dfs(j=0):
    if j == m+1: return 1
    res = 0
    for c in range(26):
        c = chr(c+97)
        ii = []
        for i, s in enumerate(ss):
            if j-jump[i] < m and s[j-jump[i]] != c:
                if jump[i]: break
                jump[i] = 1
                ii.append(i)
        else:
            res += dfs(j+1)
        for i in ii: jump[i] = 0
    return res

n, m = LI()
ss = [SI() for _ in range(n)]

# jump = [0]*n
# print(dfs())

tt = set()

t = compare(ss[0], ss[1])
# pDB(t)
if check(t): tt.add("".join(t))

t = compare(ss[1], ss[0])
# pDB(t)
if check(t): tt.add("".join(t))

print(len(tt))