import sys
readline=sys.stdin.readline
N,M=map(int,readline().split())
S=[readline().rstrip() for i in range(N)]
for j in range(M):
    if S[0][j]!=S[1][j]:
        break
se=set()
alp=[chr(i) for i in range(97,97+26)]
se.add(S[0][:j]+S[1][j]+S[0][j:])
se.add(S[1][:j]+S[0][j]+S[1][j:])
ans=0
for s in se:
    if all(S[i] in s for i in range(N)):
        ans+=1
print(ans)