XML : Complex Type definition gives a unique particle violation error

The given definition of the type MyType should allow the element sequences A; B; C; A, B and A, C. On validation I get an "unique particle violation" error. How can I fix this issue?

  <xs:complexType name="MyType">    <xs:choice>      <xs:element name="A" type="AType"/>      <xs:sequence>        <xs:element name="A" type="AType" minOccurs="0"/>        <xs:choice>          <xs:element name="B" type="BType"/>          <xs:element name="C" type="CType"/>        </xs:choice>      </xs:sequence>    </xs:choice>  </xs:complexType>