Lease agreement

Mr.A paid Rs.O to Mr.B on an agreement that Mr.B will rent out a portion of the building to Mr.C.

Mr.B did not perform as agreed to. Mr.B didnot pay the money too to Mr.A

Mr.C is not willing to sue Mr.B. 

Mr.A is not willing to take avtion against MrC.

What is the way out for Mr.A to get back the money from Mr.B legally?