#include <bits/stdc++.h>
using namespace std;
int main(){
  int N, M;
  cin >> N >> M;
  vector<string> S(N);
  for (int i = 0; i < N; i++){
    cin >> S[i];
  }
  int p = 0, q = M - 1;
  string A;
  while (p < M){
    if (S[0][p] == S[1][p]){
      A += S[0][p];
      p++;
    } else {
      break;
    }
  }
  string B;
  while (q >= 0){
    if (S[0][q] == S[1][q]){
      B += S[0][q];
      q--;
    } else {
      break;
    }
  }
  reverse(B.begin(), B.end());
  vector<string> R;
  if (S[0].substr(p + 1, q - p) == S[1].substr(p, q - p)){
    R.push_back(A + S[0][p] + S[0].substr(p + 1, q - p) + S[1][q] + B);
  }
  if (S[0].substr(p, q - p) == S[1].substr(p + 1, q - p)){
    R.push_back(A + S[1][p] + S[0].substr(p, q - p) + S[0][q] + B);
  }
  sort(R.begin(), R.end());
  R.erase(unique(R.begin(), R.end()), R.end());
  int cnt = R.size();
  int ans = 0;
  for (int i = 0; i < cnt; i++){
    bool ok = true;
    for (int j = 0; j < N; j++){
      int p2 = 0;
      for (int k = 0; k <= M; k++){
        if (p2 < M){
          if (R[i][k] == S[j][p2]){
            p2++;
          }
        }
      }
      if (p2 != M){
        ok = false;
      }
    }
    if (ok){
      ans++;
    }
  }
  cout << ans << endl;
}