import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.NoSuchElementException;

public class Main {
    static FastScanner scan = new FastScanner();
    static PrintWriter out = new PrintWriter(System.out);

    public static void main(String[] args) {
        int H = scan.nextInt();
        int W = scan.nextInt();
        char[][] map = new char[H][W];
        char[][] work = new char[H][W];
        
        int notNum = 0;
        for(int i=0; i<H; i++) {
            String line = scan.next();
            if(line.indexOf("#") < 0) {
                notNum++;
            } else {
                map[0] = line.toCharArray();
                break;
            }
        }
        H -= notNum;
        
        for(int i=1; i<H; i++) {
            map[i] = scan.next().toCharArray();
        }
        
        for(int dy=0; dy<H; dy++) {
            for(int dx=-(W-1); dx<W; dx++) {
                if(dy == 0 && dx == 0) continue;
                
                for(int k=0; k<H; k++) {
                    work[k] = map[k].clone();
                }
                
                boolean isOK = false;
                for(int i=0; i<H; i++) {
                    for(int j=0; j<W; j++) {
                        if(work[i][j] == '.') continue;                
                        int toI = i+dy;
                        int toJ = j+dx;
                        if(toI >= 0 && toJ >= 0 && toI < H && toJ < W && work[toI][toJ] == '#') {    
                            work[i][j] = '.';
                            work[toI][toJ] = '.';
                            isOK = true;
                        } else {
                            isOK = false;
                            break;
                        }
                    }
                    if(!isOK) break;
               }
               if(isOK) {
                   System.out.println("YES");
                   return;
               }
            }            
        }
        System.out.println("NO");
    }
    
    static 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;
        }

        private void skipUnprintable() {
            while (hasNextByte() && !isPrintableChar(buffer[ptr]))
                ptr++;
        }

        public boolean hasNext() {
            skipUnprintable();
            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 int nextInt() {
            return (int) nextLong();
        }

        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();
            }
        }
    }
}