B'Nicholas, a painter is going to paint several new canvases. Nicholas is sure that the canvases will turn out so great that each one will need framing and being hung on the wall. Frames are what Nicholas decided to begin with. Nicholas has n sticks whose lengths equal a1, xe2 x80 x89a2, xe2 x80 x89... an. Nicholas does not want to break the sticks or glue them together. To make a h xe2 x80 x89 xc3 x97 xe2 x80 x89w-sized frame, he needs two sticks whose lengths equal h and two sticks whose lengths equal w. Specifically, to make a square frame (when h xe2 x80 x89= xe2 x80 x89w), he needs four sticks of the same length. Now Nicholas wants to make from the sticks that he has as many frames as possible; to be able to paint as many canvases as possible to fill the frames. Help him in this uneasy task. Note that it is not necessary to use all the sticks Nicholas has. The first line contains an integer n (1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89n xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89100) -- the number of sticks. The second line contains n space-separated integers. The i-th integer equals the length of the i-th stick ai (1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89ai xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89100). Print the single number -- the maximum number of frames Nicholas can make for his future canvases.'...