#include <bits/stdc++.h>
#include <atcoder/all>
typedef long long int ll;
using namespace std;
typedef pair<ll, ll> P;
using namespace atcoder;
template<typename T> using min_priority_queue = priority_queue<T, vector<T>, greater<T>>;
#define USE998244353
#ifdef USE998244353
const ll MOD = 998244353;
// const double PI = 3.1415926535897932;
using mint = modint998244353;
#else
const ll MOD = 1000000007;
using mint = modint1000000007;
#endif
const int MAX = 2000001;
long long fac[MAX], finv[MAX], inv[MAX];
void COMinit() {
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for (int i = 2; i < MAX; i++){
        fac[i] = fac[i - 1] * i % MOD;
        inv[i] = MOD - inv[MOD%i] * (MOD / i) % MOD;
        finv[i] = finv[i - 1] * inv[i] % MOD;
    }
}
long long COM(int n, int k){
    if (n < k) return 0;
    if (n < 0 || k < 0) return 0;
    return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}
ll gcd(ll x, ll y) {
   if (y == 0) return x;
   else if (y > x) {
       return gcd (y, x); 
   }
   else return gcd(x % y, y);
}
ll lcm(ll x, ll y) {
   return x / gcd(x, y) * y;
}
ll my_sqrt(ll x) {
    // 
    ll m = 0;
    ll M = 3000000001;
    while (M - m > 1) {
        ll now = (M + m) / 2;
        if (now * now <= x) {
            m = now;
        }
        else {
            M = now;
        }
    }
    return m;
}
ll keta(ll num, ll arity) {
    ll ret = 0;
    while (num) {
        num /= arity;
        ret++;
    }
    return ret;
}
ll ceil(ll n, ll m) {
    // n > 0, m > 0
    ll ret = n / m;
    if (n % m) ret++;
    return ret;
}
ll pow_ll(ll x, ll n) {
    if (n == 0) return 1;
    if (n % 2) {
        return pow_ll(x, n - 1) * x;
    }
    else {
        ll tmp = pow_ll(x, n / 2);
        return tmp * tmp;
    }
}
vector<ll> compress(vector<ll>& v) {
    // [3 5 5 6 1 1 10 1] -> [1 2 2 3 0 0 4 0] 
    vector<ll> u = v;
    sort(u.begin(), u.end());
    u.erase(unique(u.begin(),u.end()),u.end());
    map<ll, ll> mp;
    for (int i = 0; i < u.size(); i++) {
        mp[u[i]] = i;
    }
    for (int i = 0; i < v.size(); i++) {
        v[i] = mp[v[i]];
    }
    return v;
}

vector<ll> Eratosthenes( const ll N )
{
    vector<bool> is_prime( N + 1 );
    for( ll i = 0; i <= N; i++ )
    {
        is_prime[ i ] = true;
    }
    vector<ll> P;
    for( ll i = 2; i <= N; i++ )
    {
        if( is_prime[ i ] )
        {
            for( ll j = 2 * i; j <= N; j += i )
            {
                is_prime[ j ] = false;
            }
            P.emplace_back( i );
        }
    }
    return P;
}

/* 

a[s]
b[t]

ba[s]
ab[t]

*/

// abcdef    bcded  *  a cdef  * abdef
bool contain(string& sub, string& s) {
    int m = sub.size();
    int same_f = 0;
    int same_l = 0;
    while ((same_f < m) && (sub[same_f] == s[same_f])) {
        same_f++;
    }
    while ((same_l < m) && (sub[m - 1 - same_l] == s[m - same_l])) {
        same_l++;
    }
    // cout << same_f << ' ' << same_l << '\n';
    if (same_f + same_l >= m) {
        return true;
    }
    else {
        return false;
    }
}

int main() {
    int n, m;
    cin >> n >> m;
    vector<string> ss(n);
    for (int i = 0; i < n; i++) cin >> ss[i];
    for (int i = 0; i < m; i++) {
        for (int j = 1; j < n; j++) {
            if (ss[j][i] != ss[0][i]) {
                // sub(i~m)を考えれば良い

                string s = ss[0].substr(i);
                string t = ss[j].substr(i);

                string can1 = ss[0].substr(0, i) + s[0] + t;
                string can2 = ss[0].substr(0, i) + t[0] + s;

                // cout << can1 << ' ' << can2 << '\n';

                int ok1 = 1;
                int ok2 = 1;
                for (int k = 0; k < n; k++) {
                    if (!contain(ss[k], can1)) ok1 = 0;
                }
                for (int k = 0; k < n; k++) {
                    if (!contain(ss[k], can2)) ok2 = 0;
                }

                cout << ok1 + ok2 << '\n';

                return 0;
            }
        }
    }

    unordered_set<string> us;

    for (int i = 0; i <= m; i++) {
        for (int j = 0; j < 26; j++) {
            string cur = ss[0].substr(0, i) + (char)('a' + j) + ss[0].substr(i);
            us.insert(cur);
        }
    }

    // for (auto s : us) {
    //     cout << s << '\n';
    // }

    cout << us.size() << '\n';

    // string s1 = "abcd";
    // string s2 = "aabcd";
    // contain(s1, s2);
    return 0;
}