Score : 700 points
Takahashi is playing with N cards.
The i-th card has an integer X_i on it.
Takahashi is trying to create as many pairs of cards as possible satisfying one of the following conditions:
Find the maximum number of pairs that can be created.
Note that a card cannot be used in more than one pair.
The input is given from Standard Input in the following format:
N M X_1 X_2 ... X_N
Print the maximum number of pairs that can be created.
7 5 3 1 4 1 5 9 2
3
Three pairs (3,2), (1,4) and (1,9) can be created.
It is possible to create pairs (3,2) and (1,1), but the number of pairs is not maximized with this.
15 10 1 5 6 10 11 11 11 20 21 25 25 26 99 99 99
6