#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define endl "\n"
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n, m; cin >> n >> m;
	vector<string>s(n);
	rep(i, n)cin >> s[i];
	vector<string>str(2);
	rep(i, m) {
		if (s[0][i] != s[1][i]) {
			str[0] = s[0].substr(0, i + 1);
			str[0] += s[1].substr(i);
			str[1] = s[1].substr(0, i + 1);
			str[1] += s[0].substr(i);
			break;
		}
	}
	int ans = 0;
	rep(i, 2) {
		bool chk = true;
		rep(j, n) {
			int pos = 0;
			rep(k, str[i].size()) {
				if (s[j][pos] == str[i][k]) {
					pos++;
					if (pos == m)break;
				}
			}
			if (pos != m)chk = false;
		}
		if (chk)ans++;
	}
	cout << ans << endl;
	//cout << str[0] << endl;
	//cout << str[1] << endl;
	return 0;
}