#include <iostream>
#include <vector>
#include <algorithm>
#include <map>
#include <atcoder/modint>
using namespace std;
using i32 = int;
using u32 = unsigned int;
using i64 = long long;
using u64 = unsigned long long;
#define rep(i,n) for(int i=0; i<(int)(n); i++)

using m32 = atcoder::static_modint<1000000007>;

int H,W;
map<pair<pair<int,int>, pair<int,int>>, m32> dp;
vector<string> S;

m32 recursion(int y1, int x1, int y2, int x2){
    if(y1 > y2 || x1 > x2){ return m32::raw(0); }
    if(S[y1][x1] != S[y2][x2]) return m32::raw(0);
    if(y1 + x1 + 1 >= x2 + y2) return m32::raw(1);
    if(dp.count({{y1,x1},{y2,x2}})) return dp[{{y1,x1},{y2,x2}}];
    m32 ans = 0;
    ans += recursion(y1+1, x1, y2-1, x2);
    ans += recursion(y1+1, x1, y2, x2-1);
    ans += recursion(y1, x1+1, y2-1, x2);
    ans += recursion(y1, x1+1, y2, x2-1);
    return dp[{{y1,x1},{y2,x2}}] = ans;
}

int main(){
    cin >> H >> W;
    S.resize(H);
    rep(y,H) cin >> S[y];
    m32 ans = recursion(0,0,H-1,W-1);
    cout << ans.val() << '\n';
    return 0;
}

struct ios_do_not_sync{
    ios_do_not_sync(){
        std::ios::sync_with_stdio(false);
        std::cin.tie(nullptr);
    }
} ios_do_not_sync_instance;