#!/usr/bin/python
import sys

def find_r(H, W, S):
    for y in range(H):
        for x in range(W):
            if S[y][x] == "#":
                return x, y
    print "NO"
    sys.exit(0)

def check(B, rx, ry, bx, by):
#    print rx, ry, bx, by
    cy = by - ry
    cx = bx - rx
    for y in range(H):
        for x in range(W):
            if B[y][x] == "#":
                B[y][x] = "R"
                if y+cy not in range(H):
                    return False
                if x+cx not in range(W):
                    return False
                if B[y+cy][x+cx] == "#":
                    B[y+cy][x+cx] = "B"
                else:
                    return False
    return True

def print_s(S):
    print "\n".join(["".join(x) for x in S])

H, W = map(int, raw_input().split())
#print H, W
S = []
for i in range(H):
    S.append(list(raw_input()))

rx, ry = find_r(H, W, S)
S[ry][rx] = "R"
#print rx, ry, S

for by in range(H):
    for bx in range(W):
        if S[by][bx] != "#":
            continue
        B = map(list, S)
        B[by][bx] = "B"
        if check(B, rx, ry, bx, by):
            print "YES"
#            print_s(B)
            sys.exit(0)
print "NO"