use std::collections::HashMap;

const SDX: [isize; 2] = [-1, 0];
const SDY: [isize; 2] = [0, -1];
const GDX: [usize; 2] = [1, 0];
const GDY: [usize; 2] = [0, 1];
const MOD: usize = 1e9 as usize + 7;

fn main() {
    let mut hw = String::new();
    std::io::stdin().read_line(&mut hw).ok();
    let hw: Vec<usize> = hw.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
    let h = hw[0];
    let w = hw[1];
    let grid = (0..h).map(|_| {
            let mut temp = String::new();
            std::io::stdin().read_line(&mut temp).ok();
            let temp = temp.trim();
            temp.chars().collect::<Vec<_>>()
        })
        .collect::<Vec<_>>();

    let times = (h+w)/2-1;
    let mut result = 0usize;
    let mut dp = HashMap::new();
    for i in 0..h.min(w) {
        let x = if h < w { i } else { times-i };
        let y = if h < w { times-i } else { i };
        if (h + w) % 2 == 0 {
            dp.insert((x, y, x, y), 1usize);
        } else {
            if x+1 < h && grid[x][y] == grid[x+1][y] {
                dp.insert((x, y, x+1, y), 1usize);
            }
            if y+1 < w && grid[x][y] == grid[x][y+1] {
                dp.insert((x, y, x, y+1), 1usize);
            }
        };
    }
    for _ in 0..times {
        let mut next_dp = HashMap::new();
        for (&(sx, sy, gx, gy), &cnt) in dp.iter() {
            for sdir in 0..2 {
                let nsx = sx as isize + SDX[sdir];
                let nsy = sy as isize + SDY[sdir];
                if !(nsx >= 0 && nsy >= 0) { continue; }
                let nsx = nsx as usize;
                let nsy = nsy as usize;
                for gdir in 0..2 {
                    let ngx = gx + GDX[gdir];
                    let ngy = gy + GDY[gdir];
                    if !(ngx < h && ngy < w) { continue; }
                    if grid[nsx][nsy] != grid[ngx][ngy] { continue; }
                    *next_dp.entry((nsx, nsy, ngx, ngy)).or_insert(0usize) += cnt;
                    *next_dp.entry((nsx, nsy, ngx, ngy)).or_insert(0usize) %= MOD;
                }
            }
        }
        dp = next_dp;
    }
    result += dp.values().sum::<usize>();
    result %= MOD;
    println!("{}", result);
}