#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic pop
using namespace std;
using namespace atcoder;
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; i--)
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; } else return false; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return true; } else return false; }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n, m;
  cin >> n >> m;
  vector<string> s(n);
  rep(i, n) cin >> s[i];

  int p = 0;
  while(s[0][p] == s[1][p]) p++;
  string t0 = s[0], t1 = s[1];
  t0.insert(p, 1, s[1][p]);
  t1.insert(p, 1, s[0][p]);
  int ans = 0;
  for(const string& t: {t0, t1}) {
    bool ok = true;
    for(const string& si: s) {
      int i = 0;
      for(char c: si) {
        while(i < m + 1 && c != t[i]) i++;
        if (i == m + 1) {
          ok = false;
          break;
        }
        i++;
      }
    }
    ans += ok;
  }
  cout << ans << '\n';
}