#pragma GCC target("avx2")
#pragma GCC optimize("unroll-loops")

#include <algorithm>
#include <bitset>
#include <climits>
#include <cmath>
#include <cstring>
#include <deque>
#include <forward_list>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

#define ALL(x) (x).begin(), (x).end()
#define PC(x) __builtin_popcount(x)
#define PCL(x) __builtin_popcountll(x)

using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
struct edge {
    int to, cost, id;
};
const double PI = 3.14159265358979323846;
const double PI2 = PI * 2.0;
const double EPS = 1E-09;
const ll MOD = 1E+09 + 7; // =998244353;
const ll INFL = 1E18;
const int INFI = 1E09;
const int MAX_N = 1E+06;

ll dx[4] = { -1, 1, 0, 0 }, dy[4] = { 0, 0, -1, 1 };

int N, M;

string S[MAX_N + 1];

int check(string& com, string& con, string& m1, string& m2)
{
    char x = m1.back();
    char y = m2[0];
    for (int i = 0; i + 1 < m1.size(); ++i) {
        if (m1[i] != m2[i + 1])
            return 0;
    }
    string t = com + y + m1 + con;
    for (int i = 1; i <= N; ++i) {
        int cnt = 0;
        for (int j = 0; j < t.size(); ++j) {
            if (t[j] == S[i][cnt])
                cnt++;
        }
        if (cnt < M)
            return 0;
    }
    return 1;
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    cin >> N >> M;

    for (int i = 1; i <= N; ++i) {
        cin >> S[i];
    }

    int l = 0;
    while (S[1][l] == S[2][l]) {
        ++l;
    }
    int r = M - 1;
    while (S[1][r] == S[2][r]) {
        --r;
    }

    string m1 = S[1].substr(l, r - l + 1);
    string m2 = S[2].substr(l, r - l + 1);
    string com = S[1].substr(0, l);
    string con = S[1].substr(r + 1);
    int ans = 0;
    ans += check(com, con, m1, m2);
    ans += check(com, con, m2, m1);

    // for (int i = 0; i < N; i++) {
    //     for (int j = 0; j < N; j++) {
    //         cout << "i = " << i << ", j = " << j << ", dp = " << dp[i][j] << "\n";
    //     }
    // }

    cout << ans << "\n";

    return 0;
}