>                              cell 0 is reserved 
>                              cell 1 is reserved for count
,                              the first character# ASCII digit
[                              
    >,                         read character  
    [                          swap this cell with its next cell
        -                      
        >
        +
        <
    ]
                               after this swap# original cell value should be 0
    >                          move to the next cell   
    ----------                 decrease 10# '\n' in brainfuck is 10 (in most case)
    [                          if the cell is not 0
    ++++++++++                 increase 10# reset its original value
        <                      move to the original cell
        +                      increase 1 manually# just for while loop
        >                      move to the next cell
        -                      decrease 1# because we just add 1 to original cell
        [                      loop until the next cell is 0
            <
            +
            >
            -
        ]
                               after this while loop# we reset the original cell to its original value 
    ]
    <                          but the ptr points to the next cell# we should move it to its left cell
]
<                              read completed# we are going to move to the count cell# 1
[
    <
]
>                              now move ptr to cell 2# the start of the string
[                              cut the value of cell2# paste to cell 1 and cell 0
    -
    <
    +
    <
    +
    >>
]
                               after the while statement# ptr points to cell 2
<
<
                               move ptr to cell 0 and restore cell 2# because cell 2 is start of the string
[
    -
    >
    >
    +
    <
    <
]
                               ptr points to cell 0 after while loop
>                              move it to cell 1    
                               convert ASCII code to integer# cell 1 is used for count
------------------------
------------------------
                               start print
[
    >                          move to cell 2# the start of the string
    [                          while cell has value# print it
        .
        >
    ]
                               the cell after the last cell of the string
                               we use it for printing '\n'
    ++++++++++
    .
    ----------
    
    <                          goto cell 0
    [
        <
    ]
    >                          move to cell 1# count
    -                          decrease count
]