#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); i++)
using namespace std;
using pii = pair<int, int>;
using ll = long long;

int main() {
	int n, m;
	cin >> n >> m;
	vector<string> s(n);
	rep(i, n) cin >> s[i];
	sort(s.begin(), s.end());

	rep(j, m) {
		char c = s[0][j];
		bool ok = true;
		rep(i, n) if (s[i][j] != c) ok = false;
		if (!ok) {
			rep(i, n) {
				s[i] = s[i].substr(j);
			}
			m -= j;
			break;
		}
	}

	bool ok1 = true;
	bool ok2 = true;
	string t = s[0][0] + s[n - 1];
	string u = s[n - 1][0] + s[0];
	rep(i, n) {
		int ti = 0;
		rep(si, m) {
			if (s[i][si] == t[ti]) ti++;
			else ti += 2;
			if (ti > m + 1) {
				ok1 = false;
				break;
			}
		}

		int ui = 0;
		rep(si, m) {
			if (s[i][si] == u[ui]) ui++;
			else ui += 2;
			if (ui > m + 1) {
				ok2 = false;
				break;
			}
		}
	}

	int ans = ok1 + ok2;
	if (t == u) ans = 1;
	cout << ans << endl;
	return 0;
}