#include <bits/stdc++.h>
using namespace std;
#define int long long
#define all(a) (a).begin(),(a).end()
#define rep(i, n) for(int i = 0; i < (n); i++)
#define pb push_back
#define rep1(i, n) for(int i = 1; i <= (n); i++)
#define ff first
#define ss second
const int mod = 1e9 + 7;
map<string, int> mp;
signed main() {
int n, m;
cin >> n >> m;
for (int j = 0; j < m; j++) {
string s;
cin >> s;
mp[s]++;
}
int ans = 0;
for (int i = 1; i < n; i++) {
for (int j = 0; j < m; j++) {
string s;
cin >> s;
string s1 = "", s2 = "";
for (int i = 0; i < s.size() - 1; i++) {
s1 += s[i];
}
for (int i = 1; i < s.size(); i++) {
s2 += s[i];
}
if(s1 == s2) {
if(s.size() == n) {
ans += mp[s1];
ans += mod;
ans %= mod;
}
mp[s] += mp[s1];
mp[s] += mod;
mp[s] %= mod;
}
else {
if(s.size() == n) {
ans += mp[s2] + mp[s1];
ans += mod;
ans %= mod;
}
mp[s] += mp[s2] + mp[s1];
mp[s] += mod;
mp[s] %= mod;
}
}
}
for (auto p : mp) {
string s = p.first;
int cnt = p.second;
// cout << s << ' ' << cnt << '\n';
}
cout << ans;
return 0;
}
