Rendering a shader through another

Question

I have a problem with rendering shaders. I wrote 3 shaders to create a subtraction effect: Subtractor, Platform, Slice.
Subtractor

Shader "Custom/Subtractor_Shader"
{
    SubShader
    {
        Tags { "RenderType"="Opaque" "Queue" = "Geometry-1"}

        ZWrite off

        Stencil
        {
            Ref 255
            ReadMask 3
            WriteMask 2
            Comp notequal
            Pass replace
        }

        Pass
        {
            Cull Front
            ColorMask 0
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            struct appdata
            {
                float4 vertex: POSITION;
            };

            struct v2f
            {
                float4 pos: SV_POSITION;
            };

            v2f vert(appdata v)
            {
                v2f o;
                o.pos = UnityObjectToClipPos(v.vertex);
                return o;
            }

            half4 frag(v2f i): COLOR
            {
                return half4(0,1,0,1);
            }
            ENDCG
        }
    }
}

Platform

Shader "Mobile/Fog_shader"
{
    Properties
    {
        ...
    }
    SubShader
    {
        Tags{"Queue"="Geometry"}
        Fog{ Mode off }
        LOD 200


        Stencil
        {
            ref 255
            ReadMask 2
            WriteMask 3
            Comp notequal
            Pass replace
        }

        Pass
        {
            ...
        }
    }
    Fallback "Mobile/VertexLit"
}

Slice

Shader "Custom/Slice"
{
    SubShader
    {
        Tags { "RenderType"="Opaque" "Queue" = "Geometry+1"}

        Stencil
        {
            Ref 255
            ReadMask 3
            WriteMask 3
            Comp equal
            Pass keep 
        }

        Pass
        {

            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            struct appdata
            {
                float4 vertex: POSITION;
            };

            struct v2f
            {
                float4 pos: SV_POSITION;
            };

            v2f vert(appdata v)
            {
                v2f o;
                o.pos = UnityObjectToClipPos(v.vertex);
                return o;
            }

            half4 frag(v2f i): COLOR
            {
                return half4(1,0,1,1);
            }
            ENDCG
        }
    }
}

According to my idea, the Slice should be on top of the Subtractor, but the opposite happens. What I want: What I see:

I changed the values of different shaders for Readmask and WriteMask, but it didn't help