#include<bits/stdc++.h>
#pragma GCC optimize ("-O3")
#define endl "\n"
using namespace std;
const long long nmax=2048, mod=1000000007;
long long pi[nmax];
vector<long long> a[64][nmax];
long long n, m;
long long r[nmax][nmax];
long long pw[64];
long long base=29;
bool kmp(string s, string b)
{
long long x=s.size();
s+="#"+b;
//cout<<s<<endl;
long long sz=s.size();
for(long long i=1; i<sz; ++i)
{
long long j=pi[i-1];
while(j>0&&s[i]!=s[j]) j=pi[j-1];
if(s[i]==s[j]) j++;
pi[i]=j;
if(pi[i]==x) return true;
}
return false;
}
void hashing_prefix(string s, long long i, long long j)
{
a[i][j].push_back(0);
s="%"+s;
//cout<<s<<endl;
for(long long k=1; k<(long long)s.size(); ++k)
{
a[i][j].push_back(a[i][j][k-1]*base+(s[k]-'a'+1));
a[i][j][k]%=mod;
}
//for(long long k=0; k<(long long)a[i][j].size(); ++k) cout<<a[i][j][k]<<" ";
//cout<<endl;
}
bool rabin_karp(long long i, long long j, long long i1, long long j1)
{
long long h=a[i][j][a[i][j].size()-1];
//cout<<"h = "<<h<<endl;
//cout<<(long long)a[i][j].size()<<" "<<(long long)a[i1][j1].size()<<endl;
for(long long x=1, y=(long long)a[i][j].size()-1; y<(long long)a[i1][j1].size(); ++x, ++y)
{
//cout<<"CONCALA "<<a[i1][j1][y]<<" "<<a[i1][j1][x-1]<<endl;
long long phash=a[i1][j1][y]-a[i1][j1][x-1]*pw[y-x+1];
//cout<<"ann "<<phash<<" "<<h<<endl;
phash=(phash%mod+mod)%mod;
if(h==phash) return true;
}
return false;
}
int main()
{
pw[0]=1;
for(long long i=1; i<=50; ++i) pw[i]=pw[i-1]*base, pw[i]%=mod;
string s;
cin>>n>>m;
for(long long i=0; i<n; ++i)
for(long long j=0; j<m; ++j)
{
cin>>s;
hashing_prefix(s, i, j);
}
if(n==1) cout<<m<<endl, exit(0);
for(long long i=0; i<m; ++i) r[0][i]=1;
for(long long i=0; i<n-1; ++i)
for(long long j=0; j<m; ++j)
for(long long k=0; k<m; ++k)
{
if(rabin_karp(i, j, i+1, k)) r[i+1][k]+=r[i][j], r[i+1][k]%=mod;
}
//for(long long i=1; i<n; ++i, cout<<endl)
// for(long long j=0; j<m; ++j) cout<<r[i][j]<<" ";
long long sum=0;
for(long long i=0; i<m; ++i) sum+=r[n-1][i], sum%=mod;
cout<<sum<<endl;
return 0;
}
