use std::io::Read;

fn main() {
    let mut buf = String::new();
    std::io::stdin().read_to_string(&mut buf).unwrap();
    
    let mut iter = buf.split_whitespace();
    let h: isize = iter.next().unwrap().parse().unwrap();
    let w: isize = iter.next().unwrap().parse().unwrap();
    
    let is_black: Vec<Vec<bool>> = iter.map(|s| s.chars().map(|c| c == '#').collect::<Vec<bool>>()).collect();
    let mut result: &str = "NO";
    
    'outer: for v_move in -h+1..=h-1 {
        for h_move in -w+1..=w-1 {
            if v_move == 0 && h_move == 0 { continue }
            
            let mut is_black_c: Vec<Vec<bool>> = is_black.clone();
            for i in 0..h {
                for j in 0..w {
                    let i2: isize = i + v_move;
                    let j2: isize = j + h_move;
                    if i2 >= 0 && i2 < h
                    && j2 >= 0 && j2 < w {
                        if is_black_c[i as usize][j as usize] & is_black_c[i2 as usize][j2 as usize] {
                            is_black_c[i as usize][j as usize] = false;
                            is_black_c[i2 as usize][j2 as usize] = false;
                        }
                    }
                }
            }
            
            if is_black_c.iter().all(|v| v.iter().all(|&b| !b)) {
                result = "YES";
                break 'outer;
            }
        }
    }
    if is_black.iter().all(|v| v.iter().all(|&b| !b)) {
        result = "NO";
    }
    println!("{}", result);
}