<?php
fscanf(STDIN, '%d %d', $h, $w);
$arr = [];
for($i = 0; $i < $h; $i++) {
    fscanf(STDIN, '%s', $r);
    $arr[$i][] = $r[0];
    $arr[$i][] = $r[1];
    $arr[$i][] = $r[$w-2];
    $arr[$i][] = $r[$w-1];
}
//var_dump($arr);
$b = '#'; $wh = '.';
if(($arr[0][0] == $b && $arr[0][1] == $wh && $arr[1][0] == $wh) ||
   ($arr[0][2] == $wh && $arr[0][3] == $b && $arr[1][3] == $wh) ||
   ($arr[$h-1][0] == $b && $arr[$h-2][0] == $wh && $arr[$h-1][1] == $wh) ||
   ($arr[$h-1][3] == $b && $arr[$h-2][3] == $wh && $arr[$h-1][2] == $wh) {
    echo 'No';
} else {
    echo 'Yes';
}