#include <bits/stdc++.h>


#include <algorithm>
#include <cassert>
#include <vector>

namespace rklib {

template <class T>
bool chmax(T &a, const T &b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

template <class T>
bool chmin(T &a, const T &b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}

template <class T>
bool chmin_non_negative(T &a, const T &b) {
    if (a < 0 || a > b) {
        a = b;
        return true;
    }
    return false;
}

template <class T>
T div_floor(T a, T b) {
    if (b < 0) a *= -1, b *= -1;
    return a >= 0 ? a / b : (a + 1) / b - 1;
}

template <class T>
T div_ceil(T a, T b) {
    if (b < 0) a *= -1, b *= -1;
    return a > 0 ? (a - 1) / b + 1 : a / b;
}

}  // namespace rklib


#define For(i, a, b) for (int i = (int)(a); (i) < (int)(b); ++(i))
#define rFor(i, a, b) for (int i = (int)(a)-1; (i) >= (int)(b); --(i))
#define rep(i, n) For(i, 0, n)
#define rrep(i, n) rFor(i, n, 0)
#define fi first
#define se second

using namespace std;
using namespace rklib;

using lint = long long;
using pii = pair<int, int>;
using pll = pair<lint, lint>;

bool check(string &s, string &t) {
    int j = 0;
    rep(i, s.size()) {
        while (j < int(t.size()) && s[i] != t[j]) ++j;
        if (j == int(t.size())) return false;
        ++j;
    }
    return true;
}

int main() {
    int n, m;
    cin >> n >> m;
    string s[n];
    rep(i, n) cin >> s[i];

    set<string> candidate;
    int idx = 0;
    while (s[0][idx] == s[1][idx]) ++idx;
    candidate = {s[0].substr(0, idx) + s[1][idx] + s[0].substr(idx, m - idx),
                 s[0].substr(0, idx) + s[0][idx] + s[1].substr(idx, m - idx)};
    int ans = 0;
    for (auto t : candidate) {
        bool flag = true;
        rep(i, n) if (!check(s[i], t)) {
            flag = false;
            break;
        }
        if (flag) ++ans;
    }
    printf("%d\n", ans);
}