In a glider stunt at an air show, a towing airplane (motorized plane pulling the gliders) takes off from a level runway with two gliders in tow. The gliders are pulled by two tow ropes, the first glider attached to the back of the towing plane and the second glider attached to the back of the first glider. The mass of each glider is 700 kg. The total resisting force (air drag plus friction with the runway) on each glider is equal to 3700 N. The resisting force can be assumed to be constant during the take off. The maximum allowed tension in the tow rope between the transport plane and the first glider is 12000 N. The maximum allowed tension in the second tow rope is the same as the first tow rope. If the takeoff speed for the gliders and the plane is 40 m/s, what minimum length of runway is needed for take off? Express your answer in meters.