#include <bits/stdc++.h>
using namespace std;
// bismillahirrahmanirrahim
int main() {
int N, K;
cin >> N >> K;
vector<map<string, int>> cnt(N);
for (int i = 0;i < N; ++i) {
for (int j = 0;j < K; ++j) {
string s;
cin >> s;
cnt[i][s] += 1;
}
}
if (N == 1) {
cout << K << '\n';
return 0;
}
int64_t mod = 1e9+7;
map<string, int64_t> dp;
for (int i = N-1;i >= 0; --i) {
for (auto [s, c] : cnt[i]) {
if (i == N-1) {
dp[s] = 1;
}
string a = s;
string b = s;
reverse(b.begin(), b.end());
a.pop_back();
b.pop_back();
reverse(b.begin(), b.end());
dp[a] += c * dp[s];
if (a != b) dp[b] += c * dp[s];
dp[a] %= mod;
dp[b] %= mod;
}
}
string s = "";
int64_t ans = dp[s];
cout << ans << '\n';
}
