How to get repitative group a user is member of

Hi,

i have a user in our domain who is member of number of groups. This means in MemberOF tab of the user there are larg number of groups. Now i want to remove some groups which are repitated.

Example -

1. In MemberOf Tab - properties  tab -- of John, there are 3 DL/SG "Group_1" and "Group_2" and "Group_3".   

2. Now "Group_3" is a member of "group_1". So i want to remove "Group_3" from the MemberOf Tab of John properties. This will reduce the MemberOf List.  

3. how to do i find this repetative Groups using powershell ?

Please let me know if my query is not clear.

Thanks for your help.