package main

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

var sc = bufio.NewScanner(os.Stdin)

func next() string {
	sc.Split(bufio.ScanWords)
	if !sc.Scan() {
		panic("could not scan a word from the reader")
	}
	return sc.Text()
}

func nextInt() int {
	i, e := strconv.Atoi(next())
	if e != nil {
		panic(e)
	}
	return i
}

func main() {
	H, W := nextInt(), nextInt()
	var board [110][110]bool
	for i := 0; i < H; i++ {
		row := next()
		for j, r := range row {
			if r == '#' {
				board[i][j] = true
			}
		}
	}

	check := func(dh, dw int) bool {
		var checked [110][110]bool
		var count int
		for h := 0; h < H; h++ {
			for w := 0; w < W; w++ {
				if !board[h][w] || checked[h][w] {
					continue
				}
				if !board[h+dh][w+dw] {
					return false
				}
				checked[h+dh][w+dw] = true
				count++
			}
		}
		return count > 0
	}

	for dh := 0; dh < H; dh++ {
		for dw := 0; dw < W; dw++ {
			if dh == 0 && dw == 0 {
				continue
			}
			if check(dh, dw) {
				fmt.Println("YES")
				return
			}
		}
	}
	fmt.Println("NO")
}