import sys
#input = sys.stdin.readline
#input = sys.stdin.buffer.readline #文字列はダメ
#sys.setrecursionlimit(1000000)
#import bisect
#import itertools
#import random
#from heapq import heapify, heappop, heappush
#from collections import defaultdict 
#from collections import deque
#import copy
#import math
#from functools import lru_cache
#@lru_cache(maxsize=None)
#MOD = pow(10,9) + 7
#MOD = 998244353
#dx = [1,0,-1,0]
#dy = [0,1,0,-1]
#dx8 = [1,1,0,-1,-1,-1,0,1]
#dy8 = [0,1,1,1,0,-1,-1,-1]

def main():
    N,M = map(int,input().split())
    S = set([])
    for i in range(N):
        s = input()
        S.add(s)

    if len(S) == 1:
        S = list(S)
        S = set(S[0])
        #print(S)
        if len(S) == 1:
            print(51)
        else:
            print(52)
        exit()
    
    if len(S) >= 3:
        print(0);exit()
    
    S = list(S)
    a = S[0]
    b = S[1]
    ans = 0
    if a[1:] == b[:-1]:
        ans += 1
    if b[1:] == a[:-1]:
        ans += 1
    print(ans)
  
if __name__ == '__main__':
    main()