########################################################################
#
# Part 1:   Run `cart_tick` until a collision occurs, and report the
#           location of the collision.

part_1 = lambda input_data: (
            (
                (collision % width, collision // width)
                for (tracks, carts, next_turns, width, height) in [
                    itertools.dropwhile(
                        lambda current_state: (
                            'X' not in current_state[1]
                        )
                        ,
                        accumulate(
                            itertools.chain(
                                (input_data,)
                                ,
                                itertools.count(1)
                            )
                            ,
                            lambda current_state, tick_number: (
                                cart_tick(current_state)
                            )
                        )
                    ).next()
                ]
                for collision in [
                    carts.index('X')
                ]
            ).next()
        )