// -*- coding:utf-8-unix -*-
// #![feature(map_first_last)]
#![allow(dead_code)]
#![allow(unused_imports)]
#![allow(unused_macros)]
use std::any::Any;
use std::cmp::Ordering::*;
use std::collections::*;
use std::convert::*;
use std::convert::{From, Into};
use std::error::Error;
use std::f64::consts::PI;
use std::fmt::Debug;
use std::fmt::Display;
use std::fs::File;
use std::hash::Hash;
use std::io::prelude::*;
use std::io::*;
use std::iter::Filter;
use std::marker::Copy;
use std::mem::*;
use std::ops::Bound::*;
use std::ops::RangeBounds;
use std::ops::{Add, Mul, Neg, Sub};
use std::process;
use std::slice::from_raw_parts;
use std::str;
use std::vec;

const INF: i64 = 1223372036854775807;
const UINF: usize = INF as usize;
// const FINF: f64 = 122337203685.0;
const LINF: i64 = 2147483647;
const FINF: f64 = LINF as f64;
const INF128: i128 = 1223372036854775807000000000000;
const MOD: i64 = 1000000007;
// const MOD: i64 = 998244353;
const UMOD: usize = MOD as usize;

const MPI: f64 = 3.14159265358979323846264338327950288f64;
// const MOD: i64 = INF;

use std::cmp::*;
use std::collections::*;
use std::io::stdin;
use std::io::stdout;
use std::io::Write;

macro_rules! p {
    ($x:expr) => {
        println!("{}", $x);
    };
}
macro_rules! d {
    ($x:expr) => {
        println!("{:?}", $x);
    };
}

fn main() {
    solve();
}

// use str::Chars;
#[allow(dead_code)]
fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}

#[allow(dead_code)]
fn readi() -> (i64) {
    let mut str = String::new();
    let _ = stdin().read_line(&mut str).unwrap();
    let mut iter = str.split_whitespace();
    iter.next().unwrap().parse::<i64>().unwrap()
}

#[allow(dead_code)]
fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>()
        .split_whitespace()
        .map(|e| e.parse().ok().unwrap())
        .collect()
}
#[allow(dead_code)]
fn read_mat<T: std::str::FromStr>(n: u32) -> Vec<Vec<T>> {
    (0..n).map(|_| read_vec()).collect()
}

#[allow(dead_code)]
fn readii() -> (i64, i64) {
    let mut str = String::new();
    let _ = stdin().read_line(&mut str).unwrap();
    let mut iter = str.split_whitespace();
    (
        iter.next().unwrap().parse::<i64>().unwrap(),
        iter.next().unwrap().parse::<i64>().unwrap(),
    )
}

fn readff() -> (f64, f64) {
    let mut str = String::new();
    let _ = stdin().read_line(&mut str).unwrap();
    let mut iter = str.split_whitespace();
    (
        iter.next().unwrap().parse::<f64>().unwrap(),
        iter.next().unwrap().parse::<f64>().unwrap(),
    )
}

#[allow(dead_code)]
fn readiii() -> (i64, i64, i64) {
    let mut str = String::new();
    let _ = stdin().read_line(&mut str).unwrap();
    let mut iter = str.split_whitespace();
    (
        iter.next().unwrap().parse::<i64>().unwrap(),
        iter.next().unwrap().parse::<i64>().unwrap(),
        iter.next().unwrap().parse::<i64>().unwrap(),
    )
}
#[allow(dead_code)]
fn readuu() -> (usize, usize) {
    let mut str = String::new();
    let _ = stdin().read_line(&mut str).unwrap();
    let mut iter = str.split_whitespace();
    (
        iter.next().unwrap().parse::<usize>().unwrap(),
        iter.next().unwrap().parse::<usize>().unwrap(),
    )
}

fn readcc() -> (char, char) {
    let mut str = String::new();
    let _ = stdin().read_line(&mut str).unwrap();
    let mut iter = str.split_whitespace();
    (
        iter.next().unwrap().parse::<char>().unwrap(),
        iter.next().unwrap().parse::<char>().unwrap(),
    )
}

fn readuuu() -> (usize, usize, usize) {
    let mut str = String::new();
    let _ = stdin().read_line(&mut str).unwrap();
    let mut iter = str.split_whitespace();
    (
        iter.next().unwrap().parse::<usize>().unwrap(),
        iter.next().unwrap().parse::<usize>().unwrap(),
        iter.next().unwrap().parse::<usize>().unwrap(),
    )
}
#[allow(dead_code)]
fn readiiii() -> (i64, i64, i64, i64) {
    let mut str = String::new();
    let _ = stdin().read_line(&mut str).unwrap();
    let mut iter = str.split_whitespace();
    (
        iter.next().unwrap().parse::<i64>().unwrap(),
        iter.next().unwrap().parse::<i64>().unwrap(),
        iter.next().unwrap().parse::<i64>().unwrap(),
        iter.next().unwrap().parse::<i64>().unwrap(),
    )
}

#[allow(dead_code)]
fn readuuuu() -> (usize, usize, usize, usize) {
    let mut str = String::new();
    let _ = stdin().read_line(&mut str).unwrap();
    let mut iter = str.split_whitespace();
    (
        iter.next().unwrap().parse::<usize>().unwrap(),
        iter.next().unwrap().parse::<usize>().unwrap(),
        iter.next().unwrap().parse::<usize>().unwrap(),
        iter.next().unwrap().parse::<usize>().unwrap(),
    )
}

pub fn mod_pow(x: usize, n: usize, m: usize) -> usize {
    let mut res = 1;
    let mut x = x % m;
    let mut n = n;
    while n > 0 {
        if n & 1 == 1 {
            res = (res * x) % m;
        }
        x = (x * x) % m;
        n >>= 1;
    }
    res
}
fn solve() {
    let (h, w) = readuu();
    let mut vv: Vec<Vec<char>> = vec![vec!['0' as char; (0) as usize]; (h) as usize];
    for i in 0..h {
        let s: String = read();
        let vvv = s.chars().collect();
        vv[i] = vvv;
    }
    let mut used = BTreeSet::new();
    let mut data = BTreeMap::new();
    let mut st = VecDeque::new();
    st.push_front((0, h * w - 1));
    data.insert((0, h * w - 1), 1 as usize);
    let mut res = 0;

    while !st.is_empty() {
        let (x, y) = st.pop_back().unwrap();
        if used.contains(&(x, y)) {
            continue;
        }
        used.insert((x, y));
        let cnt = *data.entry((x, y)).or_insert(0);
        let xi = (x / w) as i64;
        let xj = (x % w) as i64;
        let yi = (y / w) as i64;
        let yj = (y % w) as i64;
        if vv[xi as usize][xj as usize] != vv[yi as usize][yj as usize] {
            continue;
        }
        let dxi = vec![1, 1, 0, 0];
        let dxj = vec![0, 0, 1, 1];
        let dyi = vec![0, -1, 0, -1];
        let dyj = vec![-1, 0, -1, 0];
        if (xi - yi).abs() + (xj - yj).abs() <= 1 {
            if (xi - yi).abs() + (xj - yj).abs() == 0 {
                res += (cnt * mod_pow(2, UMOD - 1, UMOD)) % UMOD;
            } else {
                res += cnt;
            }
            res %= UMOD;
            continue;
        }
        for ii in 0..4 {
            let nxi = xi + dxi[ii];
            let nxj = xj + dxj[ii];
            let nyi = yi + dyi[ii];
            let nyj = yj + dyj[ii];
            if nxi >= 0
                && nxi < h as i64
                && nxj < w as i64
                && nxj >= 0
                && nyi >= 0
                && nyi < h as i64
                && nyj < w as i64
                && nyj >= 0
            {
                if vv[nxi as usize][nxj as usize] == vv[nyi as usize][nyj as usize] {
                    let nx = (nxi * w as i64 + nxj) as usize;
                    let ny = (nyi * w as i64 + nyj) as usize;
                    let ncnt = *data.entry((nx, ny)).or_insert(0);

                    data.insert((nx, ny), (cnt + ncnt) % UMOD);
                    st.push_front((nx, ny));
                }
            }
        }
    }

    // let res = *data.entry((h * w - 1, 0)).or_insert(0);
    println!("{}", res);
}