package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

func getScanner(fp *os.File) *bufio.Scanner {
	scanner := bufio.NewScanner(fp)
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 1000005), 1000005)
	return scanner
}
func getNextString(scanner *bufio.Scanner) string {
	scanner.Scan()
	return scanner.Text()
}
func getNextInt(scanner *bufio.Scanner) int {
	i, _ := strconv.Atoi(getNextString(scanner))
	return i
}
func getNextInt64(scanner *bufio.Scanner) int64 {
	i, _ := strconv.ParseInt(getNextString(scanner), 10, 64)
	return i
}
func getNextUint64(scanner *bufio.Scanner) uint64 {
	i, _ := strconv.ParseUint(getNextString(scanner), 10, 64)
	return i
}
func getNextFloat64(scanner *bufio.Scanner) float64 {
	i, _ := strconv.ParseFloat(getNextString(scanner), 64)
	return i
}
func main() {
	fp := os.Stdin
	wfp := os.Stdout
	cnt := 0
	if os.Getenv("MASPY") == "ますピ" {
		fp, _ = os.Open(os.Getenv("BEET_THE_HARMONY_OF_PERFECT"))
		cnt = 5
	}
	if os.Getenv("MASPYPY") == "ますピッピ" {
		wfp, _ = os.Create(os.Getenv("NGTKANA_IS_GENIUS10"))
	}
	scanner := getScanner(fp)
	writer := bufio.NewWriter(wfp)
	solve(scanner, writer)
	for i := 0; i < cnt; i++ {
		fmt.Fprintln(writer, "-----------------------------------")
		solve(scanner, writer)
	}
	writer.Flush()
}
func solve(scanner *bufio.Scanner, writer *bufio.Writer) {
	h := getNextInt(scanner)
	w := getNextInt(scanner)
	ss := make([]string, h)
	bl := 0
	for i := 0; i < h; i++ {
		ss[i] = getNextString(scanner)
		for j := 0; j < w; j++ {
			if ss[i][j] == '#' {
				bl++
			}
		}
	}
	for i := 0; i < h; i++ {
		for j := 0; j < w; j++ {
			if i+j == 0 {
				continue
			}
			p := ok(h, w, i, j, ss)
			if p<<1 == bl {
				fmt.Fprintln(writer, "YES")
				return
			}
		}
	}

	fmt.Fprintln(writer, "NO")
}

func makeGrid(h, w int) [][]bool {
	index := make([][]bool, h, h)
	data := make([]bool, h*w, h*w)
	for i := 0; i < h; i++ {
		index[i] = data[i*w : (i+1)*w]
	}
	return index
}
func ok(h, w, y, x int, ss []string) int {
	used := makeGrid(h, w)
	p := 0
	for i := 0; i+y < h; i++ {
		for j := 0; j+x < w; j++ {
			if ss[i][j] == '#' && ss[i+y][j+x] == '#' {
				if used[i][j] == false && used[i+y][j+x] == false {
					used[i][j] = true
					used[i+y][j+x] = true
					p++
				}
			}
		}
	}
	return p
}