CREATE TABLE flights
(
    from_city VARCHAR(50) NOT NULL,
    to_city   VARCHAR(50) NOT NULL,
    duration  INT         NOT NULL
);


INSERT INTO flights
    ( from_city, to_city, duration )
    VALUES
        ( 'kharkiv', 'istanbul', 120 )
      ,
        ( 'kharkiv', 'kyiv', 60 )
      ,
        ( 'kharkiv', 'lviv', 90 )
      ,
        ( 'kyiv', 'kharkiv', 30 )
      ,
        ( 'kyiv', 'lviv', 40 )
      ,
        ( 'lviv', 'vancouver', 1500 )
      ,
        ( 'kyiv', 'vancouver', 1400 )      ,
        ( 'istanbul', 'vancouver', 700 )
      -- extra test cases, not part of original task
      , ( 'kyiv', 'plovdiv', 30 )
      , ( 'plovdiv', 'istanbul', 20 )