def custom_input(self, equation):
        equation = equation.replace(' ', '')  # remove whitespace
        equation_list = []
        temp_str = ""
        for char in equation:
            if char == "(":
                equation_list.append(temp_str)
                temp_str = ""
                temp_str += char
            elif char == ")":
                temp_str += char
                equation_list.append(temp_str)
                temp_str = ""
            else:
                temp_str += char
        if temp_str:
            equation_list.append(temp_str)

        result_matrix = None
        for equation in equation_list:
            if '*' in equation:
                matrices = equation.split('*')
                matrix1 = next(matrix for matrix in self.matrices if matrix.name == matrices[0])
                matrix2 = next(matrix for matrix in self.matrices if matrix.name == matrices[1])
                result_matrix = self.multiply_matrices(matrix1.name, matrix2.name)
            elif '-' in equation:
                matrices = equation.split('-')
                matrix1 = next(matrix for matrix in self.matrices if matrix.name == matrices[0])
                matrix2 = next(matrix for matrix in self.matrices if matrix.name == matrices[1])
                result_matrix = self.subtract_matrices(matrix1.name, matrix2.name)
            elif 's' in equation:
                matrices = equation.split('s')
                matrix = next(matrix for matrix in self.matrices if matrix.name == matrices[0])
                scalar = float(matrices[1])
                result_matrix = self.scalar_multiply(matrix.name, scalar)
            elif 't' in equation:
                matrix_name = equation.split('t')[0]
                matrix = next(matrix for matrix in self.matrices if matrix.name == matrix_name)
                result_matrix = self.flip_matrix(matrix.name)
            else:
                raise ValueError(f"Invalid equation '{equation}'")

            if result_matrix is not None:
                self.matrices[self.matrices.index(next(matrix for matrix in self.matrices if matrix.name == matrix_name))] = result_matrix

        return result_matrix