input: Write a function to debug the given Python code by ensuring that the function `f1` returns a value and that the function `f2` correctly uses `f1` to compute its result. The function should print the result of calling `f2` with the argument `2`.
  
  def f1(x):
      return x + 1
  
  def f2(x):
      return f1(x) * f1(x)
  
  print(f2(2)) #Output: 9
output: def f1(x):
      return x + 1
  
  def f2(x):
      return f1(x) * f1(x)