Choose between the variables tracking and the free format reasoning which strategy would be more effective than the other one when tackling the last task considering the example task instances and explain why. The variables tracking is effective when the task has multiple instructions or statements to process and need to check the important variables for each of the step. For the free format reasoning, it works well when the task needs a complex or diverse logic that is difficult to be expressed in a specific method. In a free format reasoning step, you don't have to specify the logic, but you should specify an abstract fucntion like 'derive_answer_with_explantion' which outputs both reasons and proper answer for the situation. For the variables tracking step, you should use 'for loop' to process the multiple statements or instructions step by step, 'print()' to output intermediate steps to keep track of changes of variables.

{exemplar}