Leaders of the world's biggest economies begin a two-day G20 summit on Saturday in India's capital of New Delhi. As India hosts such a powerful group of world leaders for the first time, New Delhi has been adorned with ornamental flowers and fountains at traffic roundabouts, with a fresh coat of paint for public buildings and sidewalks were spruced up. Security is being provided by 130,000 police and para-military troops, along with anti-drone systems and cutouts of langurs to scare off monkeys, while stray dogs have been cleared from the streets. WHAT IS THE G20? The world's 20 major countries…