Android : Remove the space between two linearlayout

http://i.stack.imgur.com/QoBFg.png

The output link is above. If you see in that for linearlayout1 and linearlayout2 there would be 5dp of space how to remove it.Similarly to layout 2 ,layout 3 and layout 3, layout4.

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:id="@+id/parent"
    android:orientation="vertical" 
    tools:context="com.example.examplepro.MainActivity" >  
<LinearLayout
    android:layout_width="match_parent"
        android:layout_height="0dp"
        android:id="@+id/layout1"
        android:layout_weight="25" >    
 <Button
        android:id="@+id/btn1" 
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
       android:text="1"
       android:layout_weight="1"
       />

    <Button
        android:id="@+id/btn2"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:text="1"
        android:layout_weight="1"/>
    <Button
        android:id="@+id/btn3"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
         android:text="1"
        android:layout_weight="1"
        />
    <Button
        android:id="@+id/btn4"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
         android:text="1"
        android:layout_weight="1"/>
    </LinearLayout>
    <LinearLayout 
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:id="@+id/layout2"
        android:layout_weight="25"> 
        <Button
        android:id="@+id/btn5"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
         android:text="2"
        android:layout_weight="1"
        />
    <Button
        android:id="@+id/btn6"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"

        android:layout_weight="1"/>
    <Button
        android:id="@+id/btn7"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"

        android:layout_weight="1"
        />
    <Button
        android:id="@+id/btn8"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"

        android:layout_weight="1"/>
</LinearLayout>
   <LinearLayout 
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:id="@+id/layout3"
        android:layout_weight="25"> 
        <Button
        android:id="@+id/btn9"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
         android:text="3"
        android:layout_weight="1"
        />
    <Button
        android:id="@+id/btn10"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"

        android:layout_weight="1"/>
    <Button
        android:id="@+id/btn11"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"

        android:layout_weight="1"
        />
    <Button
        android:id="@+id/btn12"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"

        android:layout_weight="1"/>
</LinearLayout>
   <LinearLayout 
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:id="@+id/layout4"
        android:layout_weight="25"> 
        <Button
        android:id="@+id/btn13"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
         android:text="4"
        android:layout_weight="1"
        />
    <Button
        android:id="@+id/btn14"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"

        android:layout_weight="1"/>
    <Button
        android:id="@+id/btn15"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"

        android:layout_weight="1"
        />
    <Button
        android:id="@+id/btn16"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"

        android:layout_weight="1"/>
</LinearLayout>
    <LinearLayout 
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:id="@+id/layout5"
        android:layout_weight="0"> 

    <Button
        android:id="@+id/btn17"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
         android:text="5"
        android:layout_weight="1"
        />
    <Button
        android:id="@+id/btn18"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
         android:text="5"
        android:layout_weight="1"/>

    <Button
        android:id="@+id/btn19"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
         android:text="5"
        android:layout_weight="1"
        />
    <Button
        android:id="@+id/btn20"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
         android:text="5"
        android:layout_weight="1"/>

</LinearLayout>



</LinearLayout>