input: from typing import Tuple
  
  def objective_function(a: int, b: int, c: int, x: int, y: int) -> int:
      """ Calculates the objective function of a linear equation ax + by = c.
      Returns the result by subtracting the product of a, x and b, y from c.
      >>> objective_function(3, 5, 7, 2, 1)
      8
      >>> objective_function(1, 2, 3, 0, 0)
      -3
      >>> objective_function(1, 1, 2, 1, 1)
      0
      """
      return a * x + b * y - c
output:     return c - (a * x + b * y)