import std.conv, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.container, std.math, std.range, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) throw new EOFException; tokens = readln.split; } auto token = tokens[0]; tokens.popFront; return token; }
int readInt() { return readToken().to!int; }
long readLong() { return readToken().to!long; }
real readReal() { return readToken().to!real; }

void chmin(T)(ref T t, in T f) { if (t > f) t = f; }
void chmax(T)(ref T t, in T f) { if (t < f) t = f; }

int binarySearch(T)(in T[] as, in bool delegate(T) test) { int low = -1, upp = cast(int)(as.length); for (; low + 1 < upp; ) { int mid = (low + upp) >> 1; (test(as[mid]) ? low : upp) = mid; } return upp; }
int lowerBound(T)(in T[] as, in T val) { return as.binarySearch((T a) => (a < val)); }
int upperBound(T)(in T[] as, in T val) { return as.binarySearch((T a) => (a <= val)); }


int H, W;
string[] S;

bool check(int dx, int dy) {
  auto vis = new bool[][](H, W);
  foreach (x; 0 .. H) foreach (y; 0 .. W) {
    if (S[x][y] == '#' && !vis[x][y]) {
      const xx = x + dx;
      const yy = y + dy;
      if (!(0 <= xx && xx < H && 0 <= yy && yy < W && S[xx][yy] == '#' && !vis[xx][yy])) {
        return false;
      }
      vis[x][y] = vis[xx][yy] = true;
    }
  }
  return true;
}

void main() {
  try {
    for (; ; ) {
      H = readInt();
      W = readInt();
      S = new string[H];
      foreach (x; 0 .. H) {
        S[x] = readToken();
      }
      bool ans;
      if (!S.any!(any!(a => (a == '#')))) {
        goto done;
      }
      foreach (dx; -H .. +H) foreach (dy; -W .. +W) {
        if (tuple(dx, dy) > tuple(0, 0)) {
          if (check(dx, dy)) {
            ans = true;
            goto done;
          }
        }
      }
     done:
      writeln(ans ? "YES" : "NO");
    }
  } catch (EOFException e) {
  }
}