#include <bits/stdc++.h>
#define REP_(i, a_, b_, a, b, ...) for (int i = (a), END_##i = (b); i < END_##i; ++i)
#define REP(i, ...) REP_(i, __VA_ARGS__, __VA_ARGS__, 0, __VA_ARGS__)
#define ALL(x) std::begin(x), std::end(x)
using Int = long long;
using Uint = unsigned long long;
using Real = long double;

template<typename T, typename U>
inline bool chmax(T &a, U b) { return a < b and ((a = b), true); }
template<typename T, typename U>
inline bool chmin(T &a, U b) { return a > b and ((a = b), true); }
template<typename T>
inline int ssize(const T &a) { return (int) a.size(); }
template<typename T>
constexpr T kBigVal = std::numeric_limits<T>::max() / 2;

struct CastInput {
  template<typename T>
  operator T() const {
    T x;
    std::cin >> x;
    return x;
  }
  struct Sized {
    int n;
    template<typename T>
    operator T() const {
      T xs(n);
      for (auto &x: xs) std::cin >> x;
      return xs;
    }
  };
  Sized operator()(int n) const { return {n}; }
} in;

template<typename Container>
std::ostream &print_seq(const Container &seq,
                        const char *sep = " ",
                        const char *ends = "\n",
                        std::ostream &os = std::cout) {
  const auto itl = std::begin(seq), itr = std::end(seq);
  for (auto it = itl; it != itr; ++it) {
    if (it != itl) os << sep;
    os << *it;
  }
  return os << ends;
}

template<typename T>
inline std::ostream &print_one(const T &x, char endc) {
  if constexpr (std::is_same<T, bool>::value) {
    return std::cout << (x ? "Yes" : "No") << endc;
  } else {
    return std::cout << x << endc;
  }
}
template<typename T>
inline std::ostream &print(const T &x) { return print_one(x, '\n'); }
template<typename T, typename... Ts>
std::ostream &print(const T &head, Ts... tail) {
  return print_one(head, ' '), print(tail...);
}
inline std::ostream &print() { return std::cout << '\n'; }
void exit_() { std::cout.flush(), std::cerr.flush(), std::_Exit(0); }

#ifdef MY_DEBUG
#include "debug_dump.hpp"
#include "backward.hpp"
backward::SignalHandling kSignalHandling;
#else
#define DUMP(...)
#define cerr if(false)cerr
#endif

using namespace std;

Int solve() {
  int n = in, m = in;
  vector<string> S = in(n);

  auto is_subseq = [&](int j, string_view T) -> bool {
    int plen = 0, slen = 0;
    while (plen < m and S[j][plen] == T[plen]) ++plen;
    while (slen < m and S[j][m - 1 - slen] == T[m - slen]) ++slen;
    return (plen + slen >= m);
  };

  std::set < string > candidates;
  {
    int i = 0;
    while (i < m and S[0][i] == S[1][i]) ++i;
    candidates.insert(S[0].substr(0, i) + S[0][i] + S[1].substr(i));
    candidates.insert(S[0].substr(0, i) + S[1][i] + S[0].substr(i));
  }

  DUMP(candidates);
  int count = 0;
  for (const string &T: candidates) {
    bool ok = true;
    for (int j = 0; j < n; ++j) {
      if (not is_subseq(j, T)) {
        ok = false;
        break;
      }
    }
    if (ok) ++count;
  }
  return count;
}

int main() {
  std::ios::sync_with_stdio(false), cin.tie(nullptr);
  cout << std::fixed << std::setprecision(18);
  const int T = 1;//in;
  REP(t, T) { print(solve()); }
  exit_();
}