// -*- 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);
    };
}

// use str::Chars;

macro_rules! M {
    (a :expr ) => {
        M::new({ a })
    };
}
#[derive(Copy, Clone, Debug)]
pub struct M(i64);
impl M {
    fn new(x: i64) -> Self {
        M(x.rem_euclid(MOD))
    }
    fn pow(self, n: usize) -> Self {
        match n {
            0 => M::new(1),
            _ => {
                let mut a = self.pow(n >> 1);
                a *= a;
                if n & 1 == 1 {
                    a *= self;
                }
                a
            }
        }
    }
    fn inv(self) -> Self {
        self.pow((MOD - 2) as usize)
    }
}
impl std::ops::Neg for M {
    type Output = M;
    fn neg(self) -> Self::Output {
        Self::new(-self.0)
    }
}
impl std::ops::AddAssign<M> for M {
    fn add_assign(&mut self, rhs: Self) {
        self.0 += rhs.0;
        self.0 %= MOD;
    }
}
impl std::ops::AddAssign<i64> for M {
    fn add_assign(&mut self, rhs: i64) {
        *self += M::new(rhs);
    }
}
impl std::ops::AddAssign<usize> for M {
    fn add_assign(&mut self, rhs: usize) {
        *self += M::new(rhs as i64);
    }
}
impl<T> std::ops::Add<T> for M
where
    M: std::ops::AddAssign<T>,
{
    type Output = Self;
    fn add(self, other: T) -> Self {
        let mut res = self;
        res += other;
        res
    }
}
impl std::ops::SubAssign<M> for M {
    fn sub_assign(&mut self, rhs: Self) {
        self.0 -= rhs.0;
        if self.0 < 0 {
            self.0 += MOD;
        }
    }
}
impl std::ops::SubAssign<i64> for M {
    fn sub_assign(&mut self, rhs: i64) {
        *self -= M::new(rhs);
        if (*self).0 < 0 {
            self.0 += MOD;
        }
    }
}
impl std::ops::SubAssign<usize> for M {
    fn sub_assign(&mut self, rhs: usize) {
        *self -= M::new(rhs as i64);
        if (*self).0 < 0 {
            self.0 += MOD;
        }
    }
}
impl<T> std::ops::Sub<T> for M
where
    M: std::ops::SubAssign<T>,
{
    type Output = Self;
    fn sub(self, other: T) -> Self {
        let mut res = self;
        res -= other;
        res
    }
}
impl std::ops::MulAssign<M> for M {
    fn mul_assign(&mut self, rhs: Self) {
        self.0 %= MOD;

        self.0 *= (rhs.0 % MOD);
        self.0 %= MOD;
    }
}
impl std::ops::MulAssign<i64> for M {
    fn mul_assign(&mut self, rhs: i64) {
        *self *= M::new(rhs);
    }
}
impl std::ops::MulAssign<usize> for M {
    fn mul_assign(&mut self, rhs: usize) {
        *self *= M::new(rhs as i64);
    }
}
impl<T> std::ops::Mul<T> for M
where
    M: std::ops::MulAssign<T>,
{
    type Output = Self;
    fn mul(self, other: T) -> Self {
        let mut res = self;
        res *= other;
        res
    }
}
impl std::ops::DivAssign<M> for M {
    fn div_assign(&mut self, rhs: Self) {
        *self *= rhs.inv();
    }
}
impl std::ops::DivAssign<i64> for M {
    fn div_assign(&mut self, rhs: i64) {
        *self /= M::new(rhs);
    }
}
impl std::ops::DivAssign<usize> for M {
    fn div_assign(&mut self, rhs: usize) {
        *self /= M::new(rhs as i64);
    }
}
impl<T> std::ops::Div<T> for M
where
    M: std::ops::DivAssign<T>,
{
    type Output = Self;
    fn div(self, other: T) -> Self {
        let mut res = self;
        res /= other;
        res
    }
}
impl std::fmt::Display for M {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.0)
    }
}
impl std::ops::Deref for M {
    type Target = i64;
    fn deref(&self) -> &Self::Target {
        &self.0
    }
}
impl std::ops::DerefMut for M {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.0
    }
}

#[allow(dead_code)]
pub fn gcd(a: usize, b: usize) -> usize {
    if b == 0 {
        a
    } else {
        gcd(b, a % b)
    }
}
#[allow(dead_code)]
pub fn lcm(a: usize, b: usize) -> usize {
    a / gcd(a, b) * b
}
#[allow(dead_code)]
/// (gcd, x, y)
pub fn extgcd(a: i64, b: i64) -> (i64, i64, i64) {
    if b == 0 {
        (a, 1, 0)
    } else {
        let (gcd, x, y) = extgcd(b, a % b);
        (gcd, y, x - (a / b) * y)
    }
}
#[allow(dead_code)]
/// x ^ n % m
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
}

pub struct Combination {
    m: usize,
    f_table: Vec<usize>,
    moi: Vec<usize>,
}

impl Combination {
    // 0 <= size <= 10^8 is constrained.
    pub fn new(mod_num: usize, table_size: usize) -> Self {
        Self {
            m: mod_num,
            f_table: vec![0; table_size],
            moi: vec![0; 0],
        }
    }
    pub fn build(&mut self) {
        let size = self.f_table.len();
        self.f_table = self.fact_table(size, self.m);
        self.moi = self.fact_inv_table(size, self.m);
    }
    fn fact_table(&mut self, len: usize, m: usize) -> Vec<usize> {
        let mut res = vec![1; len + 1];
        for i in 1..len + 1 {
            res[i] = (i as usize * res[i - 1]) % m;
        }
        res
    }

    fn fact_inv_table(&mut self, len: usize, m: usize) -> Vec<usize> {
        let mut res = vec![1; len + 1];
        for i in 1..len + 1 {
            res[i] = (res[i - 1] * self.mod_inverse(i, m)) % m;
        }
        res
    }

    pub fn p(&mut self, n: usize, k: usize) -> i64 {
        let p = MOD as usize;
        if k == 0 {
            return 1;
        }
        if n < k {
            0
        } else {
            let (a1, e1) = self.mod_fact(n, p);
            let (a2, e2) = self.mod_fact(k, p);
            let (a3, e3) = self.mod_fact(n - k, p);
            if e1 > e2 + e3 {
                0
            } else {
                let moi = self.mod_inverse(a3 % p, p);
                (a1 * self.mod_inverse(a3 % p, p) % p) as i64
            }
        }
    }
    pub fn c(&mut self, n: usize, k: usize) -> i64 {
        let p = MOD as usize;
        if n == 0 && k == 0 {
            return 1;
        }
        if n == 0 {
            return 0;
        }
        if k == 0 {
            return 1;
        }
        if n < k {
            0
        } else {
            let (a1, e1) = self.mod_fact(n, p);
            let (a2, e2) = self.mod_fact(k, p);
            let (a3, e3) = self.mod_fact(n - k, p);
            if e1 > e2 + e3 {
                0
            } else {
                (((a1 * &self.moi[k]) % p * &self.moi[n - k]) % p) as i64
            }
        }
    }
    pub fn h(&mut self, n: usize, k: usize) -> i64 {
        return self.c(n + k - 1, k);
    }

    pub fn factorial(&mut self, n: usize) -> i64 {
        return self.p(n, n);
    }

    fn extgcd(&mut self, a: i64, b: i64) -> (i64, i64, i64) {
        if b == 0 {
            (a, 1, 0)
        } else {
            let (gcd, x, y) = extgcd(b, a % b);
            (gcd, y, x - (a / b) * y)
        }
    }
    fn mod_inverse(&mut self, a: usize, m: usize) -> usize {
        let (_, x, _) = self.extgcd(a as i64, m as i64);
        ((m as i64 + x) as usize % m) % m
    }
    fn mod_fact(&mut self, n: usize, p: usize) -> (usize, usize) {
        if n == 0 {
            (1, 0)
        } else {
            let (a, b) = self.mod_fact(n / p, p);
            let pow = b + n / p;
            if n / p % 2 != 0 {
                (a * (p - self.f_table[(n % p) as usize]) % p, pow)
            } else {
                (a * self.f_table[(n % p) as usize] % p, pow)
            }
        }
    }
}
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(),
    )
}

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 {
            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);
}