package main

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

var sc = bufio.NewScanner(os.Stdin)
var wr = bufio.NewWriter(os.Stdout)

func print(x ...interface{}) {
	fmt.Fprintln(wr, x...)
}

func nextString() string {
	sc.Scan()
	return sc.Text()
}

func nextInt() int {
	sc.Scan()
	i, err := strconv.Atoi(sc.Text())
	if err != nil {
		panic(err)
	}
	return i
}

func nextFloat() float64 {
	sc.Scan()
	i, err := strconv.ParseFloat(sc.Text(), 64)
	if err != nil {
		panic(err)
	}
	return i
}

func chmax(a *int, b int) {
	if *a < b {
		*a = b
	}
}

func chmin(a *int, b int) {
	if *a > b {
		*a = b
	}
}

func reverse(s string) string {
	rs := []rune(s)
	for i, j := 0, len(s)-1; i < j; i, j = i+1, j-1 {
		rs[i], rs[j] = rs[j], rs[i]
	}
	return string(rs)
}

var (
	H, W int
	S    []string
)

func solve(dy, dx int) bool {
	used := make([][]bool, H)
	for i := range used {
		used[i] = make([]bool, W)
	}
	ok := false
	for i := range S {
		for j := range S[i] {
			if S[i][j] == '#' && !used[i][j] {
				if i+dy >= H || j+dx >= W {
					return false
				}
				if S[i+dy][j+dx] == '#' && !used[i+dy][j+dx] {
					used[i+dy][j+dx] = true
				} else {
					return false
				}
				ok = true
			}
		}
	}
	return ok
}

func main() {
	defer wr.Flush()
	sc.Split(bufio.ScanWords)

	H, W = nextInt(), nextInt()

	S = make([]string, H)
	for i := range S {
		S[i] = nextString()
	}
	for i := 0; i < 2; i++ {
		for i := range S {
			for j := range S[i] {
				if i == 0 && j == 0 {
					continue
				}
				if solve(i, j) {
					print("YES")
					return
				}
			}
		}
		for i := range S {
			S[i] = reverse(S[i])
		}
	}
	print("NO")
}