Taulan Khatuaev

for i in range(n):
    for j in range(m):
        if field[i][j] != '.':
            valid_move = True
            for dx, dy in [(1,0),(-1,0),(0,1),(0,-1)]:
                x, y = i+dx, j+dy
                while 0 <= x < n and 0 <= y < m:
                    if field[x][y] != '.':
                        valid_move = False
                        break
                    x += dx
                    y += dy
                if not valid_move:
                    break
            if not valid_move:
                print('NO')
                exit()