CREATE TABLE table_50566 ("Tournament" CLOB, "Surface" CLOB, "Week" CLOB, "Winner and score" CLOB, "Finalist" CLOB, "Semifinalists" CLOB)

Which Surface has Semifinalists of wally masur malivai washington?
SELECT "Surface" FROM table_50566 WHERE "Semifinalists" = 'wally masur malivai washington'
SELECT "Surface" FROM "table_50566" WHERE "Semifinalists" = 'wally masur malivai washington'