#![allow(unused_mut, non_snake_case, unused_macros)]

//　高速 EOF要
//macro_rules! input {(source = $s:expr, $($r:tt)*) => {let mut iter = $s.split_whitespace();input_inner!{iter, $($r)*}};($($r:tt)*) => {let mut s = {use std::io::Read;let mut s = String::new();std::io::stdin().read_to_string(&mut s).unwrap();s};let mut iter = s.split_whitespace();input_inner!{iter, $($r)*}};}
//macro_rules! input_inner {($iter:expr) => {};($iter:expr, ) => {};($iter:expr, $var:ident : $t:tt $($r:tt)*) => {let $var = read_value!($iter, $t);input_inner!{$iter $($r)*}};}
//macro_rules! read_value {($iter:expr, ( $($t:tt),* )) => {( $(read_value!($iter, $t)),* )};($iter:expr, [ $t:tt ; $len:expr ]) => {(0..$len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()};($iter:expr, chars) => {read_value!($iter, String).chars().collect::<Vec<char>>()};($iter:expr, usize1) => {read_value!($iter, usize) - 1};($iter:expr, $t:ty) => {$iter.next().unwrap().parse::<$t>().expect("Parse error")};}
// 低速 EOF不要
macro_rules! input {(source = $s:expr, $($r:tt)*) => {let mut iter = $s.split_whitespace();let mut next = || { iter.next().unwrap() };input_inner!{next, $($r)*}};($($r:tt)*) => {let stdin = std::io::stdin();let mut bytes = std::io::Read::bytes(std::io::BufReader::new(stdin.lock()));let mut next = move || -> String{bytes.by_ref().map(|r|r.unwrap() as char).skip_while(|c|c.is_whitespace()).take_while(|c|!c.is_whitespace()).collect()};input_inner!{next, $($r)*}};}
macro_rules! input_inner {($next:expr) => {};($next:expr, ) => {};($next:expr, $var:ident : $t:tt $($r:tt)*) => {let $var = read_value!($next, $t);input_inner!{$next $($r)*}};}
macro_rules! read_value {($next:expr, ( $($t:tt),* )) => {( $(read_value!($next, $t)),* )};($next:expr, [ $t:tt ; $len:expr ]) => {(0..$len).map(|_| read_value!($next, $t)).collect::<Vec<_>>()};($next:expr, chars) => {read_value!($next, String).chars().collect::<Vec<char>>()};($next:expr, usize1) => {read_value!($next, usize) - 1};($next:expr, $t:ty) => {$next().parse::<$t>().expect("Parse error")};}

/*
 <url:https://yukicoder.me/problems/no/179>
 問題文============================================================
 =================================================================
 解説=============================================================
 ================================================================
 */

fn main() {
    input! {H:usize,W:usize,S: [chars; H]}
    let H: usize = H;
    let W: usize = W;
    let S: Vec<Vec<char>> = S;


    if !S.iter().any(|v| v.iter().any(|&c| c=='#')){
        println!("NO");
        return;
    }

    let mut flag = false;

    'solver:for sita in 0..H as i32 {
        for migi in -(W as i32)..W as i32 {
            if sita == 0 && migi == 0{
                continue;
            }
            let mut ok = true;
            let mut checked = S.clone();
            'check: for h in 0..H as i32 {
                for w in 0..W as i32 {
                    if checked[h as usize][w as usize] != '#'{
                        continue;
                    }
                    if (h as i32+sita>=0)&&(w as i32 +migi>=0)&&(h as i32 + sita < H as i32) && (w as i32 + migi < W as i32){
                        if checked[(h+sita)as usize][(w+migi) as usize] == '#'{
                            checked[h as usize][w as usize] = '@';
                            checked[(h+sita) as usize][(w+migi) as usize] = '@';
                        }else{
                            ok = false;
                            break 'check;
                        }
                    }else{
                        ok = false;
                        break 'check;
                    }
                }
            }
            if ok{
                flag = true;
                break 'solver;
            }
        }
    }
    println!("{}",if flag{"YES"}else{"NO"});
}