<prompt> Pedzisa mutsara unotevera: Mednis akapedza ari wechipiri mu1955 World Junior Championship shure kwaBoris Spassky vaviri vacho vakagadzirisa mutambo wavo. Akanga ari mutambi wokutanga kukurira Bobby Fischer muU.S. Championship. Akatamba muchikwata cheUS cha1962 pa  <response>: 15th Chess Olympiad uye vakapedza vakaenzana wechitatu mu196162 US Championship. Mhedzisiro yemakwikwi yaisanganisira yechitatu muHouston 1974, yakaenzana yechina muNew York City 1980, uye yakaenzana yekutanga muPuerto Rico 1984. Puerto Rico Chess Federation, panzvimbo peUnited States Chess Federation, yakamukurudzira zviri pamutemo nokuda kwezita reGrandmaster. Akatamba mumutambo we 1979 Interzonal muRiga, nzvimbo yake yekuzvarwa. 