Sharepoint Workflow Task completed programmatic

Hello Developers,

 

i have three types of user in workflow

1) Reviewer

2) Approver

3) Final Approver

 

And i m using three forms in workflow.

1_ Custom initiation form

2_ Custom Association form

3_ Custom task Form

 

now , i have created Individual task for all the reviewer. now what i want to do , If any one reviewer review this task , others task has to be completed automatically  using workflow . 

Have a idea about it?

Thanks in advance.