 Complete the following phrase:  Originally Raović started out as a hurdler but made a transition to sprinting. He made his international debut at the 2011 World Youth Championships in Athletics in the boys 400 meters, where he ran under the 50 second barrier. He then appeared at the 2012 World Junior Championships in Athletics, where he also ran the 400. His last major international race as a junior was the 400 at the 