input: def calculate_objective_function(a: int, b: int, c: int, x: int, y: int) -> int:
      """ Calculate the objective function of a linear equation of the form ax + by = c.
      >>> calculate_objective_function(3, 5, 7, 2, 1)
      -2
      >>> calculate_objective_function(3, 5, 7, 4, 1)
      0
      """
      return a*x + b*y - c
output:     return a*x + b*y - c