import java.util.*; import java.io.*; public class Main { public static void main(String[] args) { FastScanner sc = new FastScanner(); int h = sc.nextInt(); int w = sc.nextInt(); String[] s = new String[h]; for (int i = 0; i < h; i++) { s[i] = sc.next(); } boolean color = false; for (int i = 0; i < h; i++) { for (int j = 0; j < w; j++) { if (s[i].charAt(i) == '#') { color = true; break; } } } if (!color) { System.out.println("NO"); return; } for (int x = -w; x <= w; x++) { for (int y = -h; y <= h; y++) { if (x == 0 && y == 0) { continue; } boolean[][] check = new boolean[h][w]; boolean ok = true; for (int i = 0; i < h; i++) { for (int j = 0; j < w; j++) { if (check[i][j]) { continue; } if (s[i].charAt(j) == '.') { continue; } check[i][j] = true; int nx = j + x; int ny = i + y; if (nx < 0 || nx >= w || ny < 0 || ny >= h) { ok = false; break; } if (check[ny][nx]) { ok = false; break; } if (s[ny].charAt(nx) == '.') { ok = false; break; } check[ny][nx] = true; } } if (ok) { System.out.println("YES"); return; } } } System.out.println("NO"); } } class FastScanner { private final InputStream in = System.in; private final byte[] buffer = new byte[1024]; private int ptr = 0; private int buflen = 0; private boolean hasNextByte() { if (ptr < buflen) { return true; } else { ptr = 0; try { buflen = in.read(buffer); } catch (IOException e) { e.printStackTrace(); } if (buflen <= 0) { return false; } } return true; } private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1; } private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126; } public boolean hasNext() { while (hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++; return hasNextByte(); } public String next() { if (!hasNext()) throw new NoSuchElementException(); StringBuilder sb = new StringBuilder(); int b = readByte(); while (isPrintableChar(b)) { sb.appendCodePoint(b); b = readByte(); } return sb.toString(); } public long nextLong() { if (!hasNext()) throw new NoSuchElementException(); long n = 0; boolean minus = false; int b = readByte(); if (b == '-') { minus = true; b = readByte(); } if (b < '0' || '9' < b) { throw new NumberFormatException(); } while (true) { if ('0' <= b && b <= '9') { n *= 10; n += b - '0'; } else if (b == -1 || !isPrintableChar(b)) { return minus ? -n : n; } else { throw new NumberFormatException(); } b = readByte(); } } public int nextInt() { long nl = nextLong(); if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE) throw new NumberFormatException(); return (int) nl; } public double nextDouble() { return Double.parseDouble(next()); } }