#include <bits/stdc++.h>
#include <time.h>
//#include <random>
//#ifndef _LOCAL
//#pragma GCC optimize("-O3")
//#pragma GCC optimize("Ofast")
//#pragma GCC optimize("unroll-loops")
//#endif
#define sz(x) int(x.size())
#define in(x) freopen(x, "r", stdin)
#define out(x) freopen(x, "w", stdout)
#define N 2 * 100500
#define oo ll(1e16)
#define pii pair <int, int>
#define pll pair <ll, ll>
#define ft first
#define sd second
#define pb push_back
#define ppb pop_back
#define mp make_pair
#define el '\n'
#define elf endl
#define base ll(1e9 + 7)
#define re return
#define nins 4294967295
using namespace std;
typedef long long ll;
typedef long double ld;
//mt19937 rnd(0);
ll n, m, dp[50][1500];
string s[50][1500];
void solve() {
cin >> n >> m;
for (int i = 0; i < n; i++)
for (int j = 0; j < m; j++)
cin >> s[i][j];
for (int i = 0; i < m; i++)
dp[0][i] = 1;
for (int i = 0; i < n - 1; i++) {
for (int j1 = 0; j1 < m; j1++)
for (int j2 = 0; j2 < m; j2++)
if (int(s[i + 1][j2].find(s[i][j1])) != -1)
dp[i + 1][j2] += dp[i][j1], dp[i + 1][j2] %= base;
}
ll rs = 0;
for (int i = 0; i < m; i++)
rs += dp[n - 1][i], rs %= base;
cout << rs;
}
int main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#ifdef _LOCAL
in("input.txt");
int t = 1;
// cin >> t;
for (int i = 1; i <= t; i++) {
cout << "Test #" << i << elf;
clock_t start_time = clock();
solve();
cerr.precision(4); cerr << fixed;
cerr << elf;
cerr << "Time :: " << ld(clock() - start_time) / CLOCKS_PER_SEC << elf;
cout << elf;
}
#else
int t = 1;
// cin >> t;
while (t--) {
solve();
cout << el;
}
#endif
}
