#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define int long long
#define FOR(i, a, b) for ( int i = a ; i <= b ; i++ )
#define FORD(i, a, b) for (int i = b; i >= a; i --)
#define REP(i, n) for (int i = 0; i < n; ++i)
#define REPD(i, n) for (int i = n - 1; i >= 0; --i)
#define pii pair<int , int>
#define Lg(x) 31 - __builtin_clz(x)
#define MASK(i) (1LL << (i))
#define BIT(x, i) (((x) >> (i)) & 1)
constexpr ll LINF = (1ll << 60);
constexpr int INF = (1ll << 30);
constexpr int MAX = 2e3 + 5;
constexpr int Mod = 1e9 + 7;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
void setupIO(){
#define name "Whisper"
//Phu Trong from Nguyen Tat Thanh High School for gifted student
srand(time(NULL));
cin.tie(nullptr)->sync_with_stdio(false); cout.tie(nullptr);
//freopen(name".inp", "r", stdin);
//freopen(name".out", "w", stdout);
cout << fixed << setprecision(10);
}
template <class X, class Y>
bool minimize(X &x, const Y &y){
X eps = 1e-9;
if (x > y + eps) {x = y; return 1;}
return 0;
}
template <class X, class Y>
bool maximize(X &x, const Y &y){
X eps = 1e-9;
if (x + eps < y) {x = y; return 1;}
return 0;
}
int nGroup, nMember;
string s[51][MAX];
int Hash[51][MAX][51], Pow[MAX];
int getHash(int i, int j, int l, int r){
return (Hash[i][j][r] - Pow[r - l + 1] * Hash[i][j][l - 1] % Mod + Mod) % Mod;
}
int dp[MAX][MAX];
void add(int &x, int y){
x += y;
if (x >= Mod) x -= Mod;
}
void sub(int &x, int y){
x -= y;
if (x < 0) x += Mod;
}
#define Base 41
void Whisper(){
cin >> nGroup >> nMember;
FOR(i, 1, nGroup) FOR(j, 1, nMember) cin >> s[i][j];
Pow[0] = 1;
for (int i = 1; i <= nGroup; ++i) Pow[i] = Pow[i - 1] * Base % Mod;
FOR(i, 1, nGroup) FOR(j, 1, nMember){
for (int v = 1; v <= (int)s[i][j].size(); ++v){
Hash[i][j][v] = (Hash[i][j][v - 1] * Base + s[i][j][v - 1] - 'a' + 1) % Mod;
}
}
for (int i = 1; i <= nMember; ++i) dp[1][i] = 1;
FOR(i, 2, nGroup) FOR(cur, 1, nMember) FOR(prv, 1, nMember){
for (int v = 0; v <= 1; ++v){
if (getHash(i - 1, prv, 1, i - 1) == getHash(i, cur, v + 1, (i - 1) + v)){
add(dp[i][cur], dp[i - 1][prv]);
break;
}
}
}
int ans = 0;
for (int i = 1; i <= nMember; ++i) add(ans, dp[nGroup][i]);
cout << ans;
}
signed main(){
setupIO();
int Test = 1;
// cin >> Test;
for ( int i = 1 ; i <= Test ; i++ ){
Whisper();
if (i < Test) cout << '\n';
}
}
