input: Write a python function to get the position of rightmost set bit.
  assert get_First_Set_Bit_Pos(12) == 3
  assert get_First_Set_Bit_Pos(18) == 2
  assert get_First_Set_Bit_Pos(16) == 5
  
output: def get_First_Set_Bit_Pos(n):
      return (n & -n).bit_length()