package main

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

var sc = bufio.NewScanner(os.Stdin)
var rdr = bufio.NewReaderSize(os.Stdin, 1000000)

func main() {
	sc.Split(bufio.ScanWords)
	h, w := nextInt(), nextInt()
	m := make([][]rune, h)
	for i := range m {
		m[i] = []rune(nextLine())
	}

	n := rune(2500)
	for i := 0; i < h; i++ {
		for j := 0; j < w; j++ {
			if i == 0 && j == 0 {
				continue
			}
			isP, not := true, false
			for k, v := range m {
				for l, v2 := range v {
					if v2 == '.' || v2 == n {
						continue
					}
					not = true

					if h <= k+i || 0 > l-j {
						isP = false
						break
					}

					if m[k+i][l-j] == '.' {
						isP = false
						break
					}
					m[k+i][l-j], m[k][l] = n, n
				}
				if !isP {
					break
				}
			}

			if isP && not {
				fmt.Println("YES")
				return
			}
			n++
		}
	}

	for i := 0; i < h; i++ {
		for j := 0; j < w; j++ {
			if i == 0 && j == 0 {
				continue
			}
			isP, not := true, false
			for k, v := range m {
				for l, v2 := range v {
					if v2 == '.' || v2 == n {
						continue
					}
					not = true

					if h <= k+i || w <= l+j {
						isP = false
						break
					}

					if m[k+i][l+j] == '.' {
						isP = false
						break
					}
					m[k+i][l+j], m[k][l] = n, n
				}
				if !isP {
					break
				}
			}

			if isP && not {
				fmt.Println("YES")
				return
			}
			n++
		}
	}
	fmt.Println("NO")
}

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

func nextInt() int {
	i, _ := strconv.Atoi(nextLine())
	return i
}