//TODO
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 mut mapping: Vec<Vec<char>> = vec![];
    for _ in 0..h {
        let mut s = String::new();
        std::io::stdin().read_line(&mut s).ok();
        mapping.push(s.trim().chars().collect());
    }
    if 0 == mapping.iter().map(|col| col.iter().filter(|&c| *c == '#').count()).sum::<usize>() {
        println!("NO");
        return;
    }

    for i in 0..h {
        for j in 0..w {
            if i == 0 && j == 0 { continue; }
            for direct in vec![-1, 1].iter() {
                let mut used: Vec<Vec<bool>> = vec![vec![false; w]; h];
                let mut flg = true;
                for k in 0..h {
                    for (l, val) in mapping[k].iter().enumerate() {
                        if *val == '#' {
                            let row: usize = k + i;
                            let col: isize = l as isize + j as isize * direct;
                            if !used[k][l] {
                                if row >= h || col >= w as isize || col < 0isize || mapping[row][col as usize] != '#' {
                                    flg = false;
                                    break;
                                } else {
                                    used[row][col as usize] = true;
                                }
                            }
                        }
                    }
                    if !flg {
                        break;
                    }
                }
                if flg {
                    println!("YES");
                    return;
                }
            }
        }
    }
    println!("NO");
}