#include <iostream>
#include <sstream>
#include <iomanip>
#include <vector>
#include <string>
#include <map>
#include <set>
#include <algorithm>
#include <numeric>
#include <iterator>
#include <functional>
#include <complex>
#include <queue>
#include <stack>
#include <cmath>
#include <cassert>
#include <tuple>
using namespace std;
typedef long long LL;
typedef complex<double> CMP;
static const unsigned MODVAL = 1000000007;
struct mint
{
unsigned val;
mint():val(0){}
mint(int x):val(x%MODVAL) {}
mint(unsigned x):val(x%MODVAL) {}
mint(LL x):val(x%MODVAL) {}
};
mint& operator+=(mint& x, mint y) { return x = x.val+y.val; }
mint& operator-=(mint& x, mint y) { return x = x.val-y.val+MODVAL; }
mint& operator*=(mint& x, mint y) { return x = LL(x.val)*y.val; }
mint operator+(mint x, mint y) { return x+=y; }
mint operator-(mint x, mint y) { return x-=y; }
mint operator*(mint x, mint y) { return x*=y; }
class CampLunch { public:
int count(int N, int M, vector <string> a)
{
memo.assign(N<<M, -1);
memo2.assign(N*M<<M, -1);
return rec(N, M, a, 0, 0);
}
vector<int> memo;
int rec(int N, int M, const vector<string>& A, int d, int yesterday_free) {
if(d == N)
return 1;
const int key = (d<<M) | yesterday_free;
if(memo[key] >= 0)
return memo[key];
return memo[key] = rec2(N, M, A, d, 0, yesterday_free, 0);
}
vector<int> memo2;
int rec2(int N, int M, const vector<string>& A,
int d, int i, int yesterday_free, int today_free) {
if(i == M)
return rec(N,M,A,d+1,today_free);
const int key = ((d*M+i)<<M) | yesterday_free | today_free;
if(memo2[key] >= 0)
return memo2[key];
mint total = 0;
// Plan 2.
int p = A[d][i] - 'A';
if(yesterday_free & (1<<p))
total += rec2(N,M,A,d,i+1,yesterday_free&~(1<<p),today_free);
// Plan 1.
if(i+1<M) {
int p2 = A[d][i+1]-'A';
total += rec2(N,M,A,d,i+2,yesterday_free&~(1<<p)&~(1<<p2),today_free);
}
// No Plan.
total += rec2(N,M,A,d,i+1,yesterday_free&~(1<<p),today_free|(1<<p));
return memo2[key] = total.val;
}
};
// BEGIN CUT HERE
#include <ctime>
double start_time; string timer()
{ ostringstream os; os << " (" << int((clock()-start_time)/CLOCKS_PER_SEC*1000) << " msec)"; return os.str(); }
template<typename T> ostream& operator<<(ostream& os, const vector<T>& v)
{ os << "{ ";
for(typename vector<T>::const_iterator it=v.begin(); it!=v.end(); ++it)
os << '\"' << *it << '\"' << (it+1==v.end() ? "" : ", "); os << " }"; return os; }
void verify_case(const int& Expected, const int& Received) {
bool ok = (Expected == Received);
if(ok) cerr << "PASSED" << timer() << endl; else { cerr << "FAILED" << timer() << endl;
cerr << "\to: \"" << Expected << '\"' << endl << "\tx: \"" << Received << '\"' << endl; } }
#define CASE(N) {cerr << "Test Case #" << N << "..." << flush; start_time=clock();
#define END verify_case(_, CampLunch().count(N, M, a));}
int main(){
CASE(0)
int N = 2;
int M = 2;
string a_[] = {"AB","AB"};
vector <string> a(a_, a_+sizeof(a_)/sizeof(*a_));
int _ = 7;
END
CASE(1)
int N = 2;
int M = 3;
string a_[] = {"ABC","ABC"};
vector <string> a(a_, a_+sizeof(a_)/sizeof(*a_));
int _ = 22;
END
CASE(2)
int N = 2;
int M = 3;
string a_[] = {"ABC","BAC"};
vector <string> a(a_, a_+sizeof(a_)/sizeof(*a_));
int _ = 21;
END
CASE(3)
int N = 1;
int M = 1;
string a_[] = {"A"};
vector <string> a(a_, a_+sizeof(a_)/sizeof(*a_));
int _ = 1;
END
CASE(4)
int N = 1;
int M = 10;
string a_[] = {"ABDEFHIGJC"};
vector <string> a(a_, a_+sizeof(a_)/sizeof(*a_));
int _ = 89;
END
CASE(5)
int N = 16;
int M = 16;
string a_[] = {"ABCDEFGHIJKLMNOP","ABCDEFGHIJKLMNOP","ABCDEFGHIJKLMNOP","ABCDEFGHIJKLMNOP","ABCDEFGHIJKLMNOP","ABCDEFGHIJKLMNOP","ABCDEFGHIJKLMNOP","ABCDEFGHIJKLMNOP","ABCDEFGHIJKLMNOP","ABCDEFGHIJKLMNOP","ABCDEFGHIJKLMNOP","ABCDEFGHIJKLMNOP","ABCDEFGHIJKLMNOP","ABCDEFGHIJKLMNOP","ABCDEFGHIJKLMNOP","ABCDEFGHIJKLMNOP"};
vector <string> a(a_, a_+sizeof(a_)/sizeof(*a_));
int _ = 950052677;
END
/*
CASE(6)
int N = ;
int M = ;
string a_[] = ;
vector <string> a(a_, a_+sizeof(a_)/sizeof(*a_));
int _ = ;
END
CASE(7)
int N = ;
int M = ;
string a_[] = ;
vector <string> a(a_, a_+sizeof(a_)/sizeof(*a_));
int _ = ;
END
*/
}
// END CUT HERE