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import java.io.*;
import java.util.*;
import java.lang.*;
    public class templ {
        public static int a[]=new int[1000000];
    int binarySearch(long arr[], int l, int r, long x)
    {
        if (r >= l)
        {
            int mid = l + (r - l)/2;
            if (arr[mid] == x)
            return mid;
            if (arr[mid] > x) 
            return binarySearch(arr, l, mid-1, x);
            return binarySearch(arr, mid+1, r, x);
        }
        return -1;
    }
    int partition(int arr[],int a[], int low, int high)
    {
        int pivot = arr[high]; 
        int i = (low-1);
        for (int j=low; j<high; j++)
        {
            if (arr[j] <= pivot)
            {
                i++;
                int temp = arr[i];
                arr[i] = arr[j];
                arr[j] = temp;
                temp = a[i];
                a[i] = a[j];
                a[j] = temp;
            }
        }
        int temp = arr[i+1];
        arr[i+1] = arr[high];
        arr[high] = temp;
        temp = a[i+1];
        a[i+1] = a[high];
        a[high] = temp;
 
        return i+1;
    }
    void sort(int arr[],int a[], int low, int high)
    {
        if (low < high)
        {
            int pi = partition(arr,a, low, high);
            sort(arr, a,low, pi-1);
            sort(arr,a, pi+1, high);
        }
    }
    public static void main(String[] args) throws FileNotFoundException {
     try
     {
        InputReader in = new InputReader(System.in);
        PrintWriter out = new PrintWriter(System.out);
        templ ob=new templ();
        int n=in.nextInt();
        int m=in.nextInt();
        String s[]=new String[n];
        int q=0;
        s[q]=in.nextLine();
        q++;
        for(int i=1;i<n;i++)
        {
            int p=0;
            String s1=in.nextLine();
            for(int j=0;j<i;j++)
            {
                if(s1.equals(s[j]))
                {
                    p=1;
                    break;
                }
            }
            if(p==0)
            {
                s[q]=s1;
                q++;
            }
        }
        int a[]=new int[m];
        for(int i=0;i<m;i++)
            a[i]=0;
        int y=0;
        for(int i=0;i<q;i++)
        {
            for(int j=0;j<s[i].length();j++)
            {
                char c=s[i].charAt(j);
                if(c=='#')
                {
                    a[j]++;
                }
            }
        }
        for(int i=0;i<m;i++)
        {
            if(a[i]>1)
            {
                y=1;
                break;
            }
        }
        if(y==1)
            out.println("No");
        else
            out.println("Yes");
        out.close();
    }
        catch(Exception e){
        return;
    }
    }
    static class InputReader {

        private final InputStream stream;
        private final byte[] buf = new byte[8192];
        private int curChar, snumChars;

        public InputReader(InputStream stream) {
            this.stream = stream;
        }

        public int read() {
            if (snumChars == -1)
                throw new InputMismatchException();
            if (curChar >= snumChars) {
                curChar = 0;
                try {
                    snumChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (snumChars <= 0)
                    return -1;
            }
            return buf[curChar++];
        }

        public int nextInt() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            int res = 0;
            do {
                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 {
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public int[] nextIntArray(int n) {
            int a[] = new int[n];
            for (int i = 0; i < n; i++) {
                a[i] = nextInt();
            }
            return a;
        }

        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 String nextLine() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            } while (!isEndOfLine(c));
            return res.toString();
        }

        public boolean isSpaceChar(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        private boolean isEndOfLine(int c) {
            return c == '\n' || c == '\r' || c == -1;
        }

    }
} 	