PITTSBURGH (AP) -- Even as President Obama arrives in Pittsburgh for the Group of 20 summit, protesters and police are clashing on the streets after police tried to break up a march opposing the meeting. Protesters rolled trash bins toward police and a man in a black hooded sweat shirt threw rocks at a police car, breaking the front windshield. Some protesters also are using pallets and corrugated steel to block a road. Officers fired gas at the protesters. Some of those exposed to the gas were coughing, complaining of eyes watering and stinging. The march began with several hundred...