 Complete the following phrase:  Ryszard Oborski born 2 May 1952 in Poznań is a Polish sprint canoer who competed from the mid-1970s to the mid-1980s. He won ten medals at the ICF Canoe Sprint World Championships with three golds K-2 500 m: 1974, K-4 500 m: 1977, K-4 1000 m: 1977, two silvers K-4 1000 m: 1979, K-4 10000 m: 1981, and five bronzes K-1 4 x 500 m: 