use std::io::{stdin, stdout, StdinLock, StdoutLock, BufReader, BufWriter, BufRead, Write};

fn main() {
    let (std_in, std_out) = (stdin(), stdout());
    let mut io = IO::new(std_in.lock(), std_out.lock());
    let tmp = io.rv::<i32>();
    let (h, w) = (tmp[0], tmp[1]);
    let mut tab = Vec::new();
    for _ in 0..h {
        tab.push(io.rb());
    }

    let mut one = false;
    for dy in -h..h {
        for dx in -w..w {
            if dy == 0 && dx == 0 {
                continue;
            }
            let mut complete = true;
            let mut t = tab.clone();
            for i in 0..h {
                for j in 0..w {
                    if t[i as usize][j as usize] != '#' as u8 {
                        continue;
                    }
                    one = true;
                    let ny = i + dy ;
                    let nx = j + dx;
                    if ny < 0 || nx < 0 || ny >= h || nx >= w || t[ny as usize][nx as usize] != '#' as u8 {
                        complete = false;
                        break;
                    }
                    t[ny as usize][nx as usize] = 0;
                }
            }
            if complete && one {
                io.w("YES");
                return;
            }
        }
    }
    io.w("NO");
}


struct IO<'a> {
    br: BufReader<StdinLock<'a>>,
    bw: BufWriter<StdoutLock<'a>>,
}

#[allow(dead_code)]
impl IO<'_> {
    fn new<'a>(il: StdinLock<'a>, ol: StdoutLock<'a>) -> IO<'a> {
        IO {br: BufReader::new(il), bw: BufWriter::new(ol) }
    }

    fn r<T: std::str::FromStr>(&mut self) -> T {
        let mut buf = String::new();
        self.br.read_line(&mut buf).ok();
        buf.trim().parse().ok().unwrap()
    }

    fn rb(&mut self) -> Vec<u8> {
        let mut buf = String::new();
        self.br.read_line(&mut buf).ok();
        buf.trim().as_bytes().to_vec()
    }

    fn rv<T: std::str::FromStr>(&mut self) -> Vec<T> {
        let mut buf = String::new();
        self.br.read_line(&mut buf).ok();
        buf.trim().split_whitespace().map(|e| e.parse().ok().unwrap()).collect()
    }

    fn rvb(&mut self) -> Vec<Vec<u8>> {
        let mut buf = String::new();
        self.br.read_line(&mut buf).ok();
        buf.trim().split_whitespace().map(|e| e.as_bytes().to_vec()).collect()
    }

    fn w<T: std::fmt::Display>(&mut self, x: T) {
        let _ = writeln!(self.bw, "{}", x);
    }

    fn wb(&mut self, s: &[u8]) {
        let _ = writeln!(self.bw, "{}", unsafe{std::str::from_utf8_unchecked(s)});
    }

    fn wv<T: std::fmt::Display>(&mut self, v: &[T]) {
        let _ = write!(self.bw, "{}", v[0].to_string());
        for x in v[1..].iter() {
            let _ = write!(self.bw, " {}", x.to_string());
        }
        let _ = writeln!(self.bw);
    }

    fn wvb(&mut self, v: &[Vec<u8>]) {
        let _ = write!(self.bw, "{}", unsafe{std::str::from_utf8_unchecked(&v[0])});
        for x in v[1..].iter() {
            let _ = write!(self.bw, " {}", unsafe{std::str::from_utf8_unchecked(x)});
        }
        let _ = writeln!(self.bw);
    }
}