CREATE TABLE table_56776 ("Year" TEXT, "League" TEXT, "Reg. Season" TEXT, "Playoffs" TEXT, "Avg. attendance" FLOAT)

Which league had a playoffs result of a lost semifinal?
SELECT "League" FROM table_56776 WHERE "Playoffs" = 'lost semifinal'
SELECT "League" FROM "table_56776" WHERE "Playoffs" = 'lost semifinal'