Direction: fly north to 10 meter, then fly east to 10 meter, then fly to 10 meter, and fly 30 meters on a broken line.

Hui: It's diagonal to the nest, and it's not right to open the Pythagorean theorem of right triangle.: Find the equation √ (20+ 10) = 10 √ 5m.

The total number of return flights is (30+10√5) meters.