#include <bits/stdc++.h>
#define fi first
#define se second
#define pb push_back
#define sz(a) (int)a.size()
#define all(a) a.begin(),a.end()
#define rep(i,n) for(int i=0;i<n;i++)
#define crep(i,x,n) for(int i=x;i<n;i++)
#define drep(i,n) for(int i=n-1;i>=0;i--)
#define vec(...) vector<__VA_ARGS__>
#define _3qplfh5 ios_base::sync_with_stdio(false),cin.tie(0),cout.tie(0)
using namespace std;
typedef long long ll;
typedef long double ld;
void print(){
cout<<"\n";
}
template<class te,class ...ti>
void print(const te&v, const ti&...nv) {
cout<<v;
if(sizeof...(nv)){
cout<<" ";
print(nv...);
}
}
using pii=pair<int,int>;
using vi=vector<int>;
using vll=vector<long long>;
//snuke's mod int
template <ll mod>
struct modint{
ll x; // typedef long long ll;
modint(ll x=0):x((x%mod+mod)%mod){}
modint operator-()const{ return modint(-x);}
modint& operator+=(const modint a){ if((x+=a.x)>=mod) x-=mod; return *this; }
modint& operator-=(const modint a){ if((x+=mod-a.x)>=mod) x-=mod; return *this; }
modint& operator*=(const modint a){ (x*=a.x)%=mod; return *this; }
modint operator+(const modint a)const{ modint res(*this); return res+=a; }
modint operator-(const modint a)const{ modint res(*this); return res-=a; }
modint operator*(const modint a)const{ modint res(*this); return res*=a; }
modint pow(ll n) const {
modint res=1,x(*this);
while(n){
if(n&1)res*=x;
x*=x;
n>>=1;
}
return res;
}
modint inv() const { return pow(mod-2); }
};
using mint=modint<1000000007>;
// include mint here
using hshmint=modint<1000000007>;
using hshmint1=modint<998244353>;
using magicpair = pair<hshmint,hshmint1>;
struct rollhsh{
hshmint _p=9973; // base
hshmint1 _p1=257; // base1
vec(hshmint) pw,invpw;
vec(hshmint1) pw1,invpw1;
vec(magicpair) hsh;
rollhsh(string s=""){
init(s);
}
void init(string s){
hsh.clear();
pw.clear();
invpw.clear();
pw1.clear();
invpw1.clear();
hsh.resize(sz(s)+1);
pw.resize(sz(s)+1);
invpw.resize(sz(s)+1);
pw1.resize(sz(s)+1);
invpw1.resize(sz(s)+1);
hsh[0]={1,1};
pw[0]=1;
pw1[0]=1;
invpw[0]=1;
invpw1[0]=1;
hshmint _invbase=_p.x;
hshmint1 _invbase1=_p1.x;
_invbase=_invbase.inv(); _invbase1=_invbase1.inv();
rep(i,sz(s)){
pw[i+1]=pw[i]*_p;
pw1[i+1]=pw1[i]*_p1;
invpw[i+1]=invpw[i]*_invbase;
invpw1[i+1]=invpw1[i]*_invbase1;
hshmint x=(int)(s[i]-'a'+1);
hshmint1 x1=(int)(s[i]-'a'+1);
hsh[i+1]={hsh[i].fi+pw[i]*x,hsh[i].se+pw1[i]*x1};
}
}
pair<ll,ll> get(int l,int r){
// from - to , inclusive
hshmint _f=invpw[l]*(hsh[r+1].fi-hsh[l].fi);
hshmint1 _s=invpw1[l]*(hsh[r+1].se-hsh[l].se);
return {_f.x,_s.x};
}
};
using pll=pair<ll,ll>;
void slv(){
int n,m;
cin>>n>>m;
vec(mint) dp(m),nedp;
vec(pll) rbts,nerbts;
rollhsh hsh;
rep(i,n){
nerbts={};
nedp=vec(mint)(m,0);
rep(j,m){
string s;
cin>>s;
hsh.init(s);
nerbts.pb(hsh.get(0,i));
if(!i){
nedp[j]=1;
}else{
rep(j1,m){
if(rbts[j1]==hsh.get(0,i-1) or rbts[j1]==hsh.get(1,i)){
nedp[j]+=dp[j1];
}
}
}
}
swap(dp,nedp);
swap(rbts,nerbts);
}
mint ans=0;
rep(j,m)
ans+=dp[j];
print(ans.x,'\n');
}
int main(){
_3qplfh5;
int t=1;
// cin>>t;
rep(cs,t)
slv();
//
return 0;
}
