def move_ok(_S, H, W, count, diff):
    S = [[_S[i][j] for j in range(W)] for i in range(H)]
    for i in range(H):
        for j in range(W):
            if S[i][j] == ".":
                continue
            elif i+diff[0] < H and j+diff[1] < W \
                and S[i+diff[0]][j+diff[1]] == "#":
                count -= 2
                S[i+diff[0]][j+diff[1]] = "."
    return count == 0

def main():
    H, W = map(int, input().split(" "))
    S = []
    for i in range(H):
        S.append(list(input()))
    start = [-1,-1]
    count = 0
    for i in range(H):
        count += S[i].count("#")
        if start[0] == -1:
            for j in range(W):
                if S[i][j] == "#":
                    start[0] = i
                    start[1] = j
                    break
    if count % 2 != 0:
        print("NO")
        return

    for i in range(H):
        for j in range(W):
            if start[0] == i and start[1] == j:
                continue
            if S[i][j] == ".":
                continue
            diff = (i-start[0], j-start[1])
            if move_ok(S, H, W, count, diff):
                print("YES")
                return
    print("NO")

if __name__ == "__main__":
    main()