CREATE TABLE table_31553 ("Date" CLOB, "Venue" CLOB, "Score" CLOB, "Result" CLOB, "Competition" CLOB)

What score did vasil levski national stadium, sofia, which was friendly during competition, earn?
SELECT "Score" FROM table_31553 WHERE "Competition" = 'friendly' AND "Venue" = 'vasil levski national stadium, sofia'
SELECT "Score" FROM "table_31553" WHERE "Competition" = 'friendly' AND "Venue" = 'vasil levski national stadium, sofia'