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/*Tough one

------------------------------------------------------------

-----------------------------------------------------------

----------------------------------------------------------*/
					import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.InputMismatchException;
									public class Solution1 implements Runnable
									{
										static final long MAX = 1000000007L;
										static class InputReader
										{
											private InputStream stream;
											private byte[] buf = new byte[1024];
											private int curChar;
											private int numChars;
											private SpaceCharFilter filter;
											private BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
									 
											public InputReader(InputStream stream)
											{
												this.stream = stream;
											}
											
											public int read()
											{
												if (numChars==-1) 
													throw new InputMismatchException();
												
												if (curChar >= numChars)
												{
													curChar = 0;
													try 
													{
														numChars = stream.read(buf);
													}
													catch (IOException e)
													{
														throw new InputMismatchException();
													}
													
													if(numChars <= 0)				
														return -1;
												}
												return buf[curChar++];
											}
										 
											public String nextLine()
											{
												String str = "";
									            try
									            {
									                str = br.readLine();
									            }
									            catch (IOException e)
									            {
									                e.printStackTrace();
									            }
									            return str;
											}
											public int nextInt()
											{
												int c = read();
												
												while(isSpaceChar(c)) 
													c = read();
												
												int sgn = 1;
												
												if (c == '-') 
												{
													sgn = -1;
													c = read();
												}
												
												int res = 0;
												do 
												{
													if(c<'0'||c>'9') 
														throw new InputMismatchException();
													res *= 10;
													res += c - '0';
													c = read();
												}
												while (!isSpaceChar(c)); 
												
												return res * sgn;
											}
											
											public long nextLong() 
											{
												int c = read();
												while (isSpaceChar(c))
													c = read();
												int sgn = 1;
												if (c == '-') 
												{
													sgn = -1;
													c = read();
												}
												long res = 0;
												
												do 
												{
													if (c < '0' || c > '9')
														throw new InputMismatchException();
													res *= 10;
													res += c - '0';
													c = read();
												}
												while (!isSpaceChar(c));
													return res * sgn;
											}
											
											public double nextDouble() 
											{
												int c = read();
												while (isSpaceChar(c))
													c = read();
												int sgn = 1;
												if (c == '-') 
												{
													sgn = -1;
													c = read();
												}
												double res = 0;
												while (!isSpaceChar(c) && c != '.') 
												{
													if (c == 'e' || c == 'E')
														return res * Math.pow(10, nextInt());
													if (c < '0' || c > '9')
														throw new InputMismatchException();
													res *= 10;
													res += c - '0';
													c = read();
												}
												if (c == '.') 
												{
													c = read();
													double m = 1;
													while (!isSpaceChar(c)) 
													{
														if (c == 'e' || c == 'E')
															return res * Math.pow(10, nextInt());
														if (c < '0' || c > '9')
															throw new InputMismatchException();
														m /= 10;
														res += (c - '0') * m;
														c = read();
													}
												}
												return res * sgn;
											}
											
											public String readString() 
											{
												int c = read();
												while (isSpaceChar(c))
													c = read();
												StringBuilder res = new StringBuilder();
												do 
												{
													res.appendCodePoint(c);
													c = read();
												} 
												while (!isSpaceChar(c));
												
												return res.toString();
											}
										 
											public boolean isSpaceChar(int c) 
											{
												if (filter != null)
													return filter.isSpaceChar(c);
												return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
											}
										 
											public String next() 
											{
												return readString();
											}
											
											public interface SpaceCharFilter 
											{
												public boolean isSpaceChar(int ch);
											}
										}
									 	
										public static void main(String args[]) throws Exception
										{
											new Thread(null, new Solution1(),"Solution1",1<<26).start();
										}
										long gcd(long a, long b)
									    {
									        if (a == 0)
									            return b;
									         
									        return gcd(b%a, a);
									    }
									    // method to return LCM of two numbers
										 long lcm(long a, long b)
										    {
										        return (a*b)/gcd(a, b);
										    }
										
										public void run()
										{
											InputReader sc= new InputReader(System.in);
											PrintWriter w= new PrintWriter(System.out);
											 int n = sc.nextInt();
									            int m = sc.nextInt();
									            char[][] ch = new char[n][m];
									            for(int i = 0;i < n;i++){
									            	String st = sc.next();
									            	ch[i] = st.toCharArray();
									            }
									            ArrayList<Integer> ar[] = new ArrayList[n];
									            for(int i = 0;i < n;i++){
									            	ar[i] = new ArrayList();
									            	for(int j = 0;j < m;j++){
									            		if(ch[i][j] == '#'){
									            			ar[i].add(j);
									            		}
									            	}
									            	for(int j = i-1;j >= 0;j--){
									            		if(ar[i].size() == ar[j].size()){
									            			int count = 0;
									            			for(int k = 0;k < ar[i].size();k++){
									            				if(ar[i].get(k) == ar[j].get(k)){
									            					count++;
									            				}
									            			}
									            			if(count > 0 && count < ar[i].size()){
									            				w.println("no");
									            				w.close();
									            				System.exit(0);
									            			}
									            		}else{
									            			for(int k = 0;k < ar[i].size();k++){
									            				if(ar[j].contains(ar[i].get(k))){
									            					w.println("no");
									            					w.close();
									            					System.exit(0);
									            				}
									            			}
									            		}
									            	}
									            }
									            w.println("yes");
									            w.close();

										}
										
										static class Pair implements Comparable<Pair>{
											int a;
											int b;
											
											Pair(){}	
											Pair(int a,int b){
												this.a = a;
												this.b = b;
												
											}
											public int compareTo(Pair p){
												return Integer.compare(this.b,p.b);
											}
										}
						}