/* -*- coding: utf-8 -*-
 *
 * 1909.cc:  No.1909 Detect from Substrings - yukicoder
 */

#include<cstdio>
#include<algorithm>
 
using namespace std;

/* constant */

const int MAX_N = 1000;
const int MAX_NM = 1000000;

/* typedef */

/* global variables */

char buf[MAX_NM + 4], *ss[MAX_N];
char t0[MAX_NM + 4], t1[MAX_NM + 4];

/* subroutines */

bool issubstr(int m, char t[], char s[]) {
  int j = 0;
  for (int i = 0; i < m + 1 && j < m; i++)
    if (t[i] == s[j]) j++;
  return (j == m);
}

bool check(int n, int m, char t[]) {
  for (int i = 0; i < n; i++)
    if (! issubstr(m, t, ss[i])) return false;
  return true;
}

/* main */

int main() {
  int n, m;
  scanf("%d%d", &n, &m);

  for (int i = 0; i < n; i++) {
    ss[i] = buf + m * i;
    scanf("%s", ss[i]);
  }
  //puts(buf);

  int k = 0;
  while (ss[0][k] == ss[1][k]) k++;
  //printf("k=%d\n", k);

  copy(ss[0], ss[0] + k + 1, t0);
  copy(ss[1] + k, ss[1] + m, t0 + k + 1);
  copy(ss[1], ss[1] + k + 1, t1);
  copy(ss[0] + k, ss[0] + m, t1 + k + 1);
  //printf("t0=%s, t1=%s\n", t0, t1);
  
  int c = 0;
  if (check(n, m, t0)) c++;
  if (check(n, m, t1)) c++;

  printf("%d\n", c);
  return 0;
}