#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];

	string t, u;
	rep(i, m) {
		if (s[0][i] != s[1][i]) {
			t = s[0].substr(0, i) + s[0][i] + s[1].substr(i);
			u = s[1].substr(0, i) + s[1][i] + s[0].substr(i);
			break;
		}
	}

	int ok1 = 1, ok2 = 1;
	rep(i, n) {
		int si = 0, ti = 0;
		while (ti < m + 1) {
			if (s[i][si] == t[ti]) si++;
			ti++;
		}
		if (si != m) ok1 = 0;

		si = 0;
		rep(ui, m + 1) {
			if (s[i][si] == u[ui]) si++;
		}
		if (si != m) ok2 = 0;
	}

	int ans = ok1 + ok2;
	cout << ans << endl;
	return 0;
}