 Complete the following phrase:  Manfred Schubert is a retired East German slalom canoeist who competed in the 1950s and 1960s. He won twelve medals at the ICF Canoe Slalom World Championships with four golds C-1: 1957, 1961, 1963; C-1 team: 1963, six silvers C-1: 1959; C-1 team: 1955, 1957, 1959, 1961, 1967, and two bronzes C-1: 