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Problems

Squares

Squares

Given the length of n segments. What is the maximum number of squares can be constructed? Each side of a square must be constructed from only one segment.

Input

The first line contains the number of segments n (1n106). The second line contains n integers - the length of segments with values no more than 100.

Output

Print the maximum number of squares that can be constructed from the given segments.

Time limit 2 seconds
Memory limit 128 MiB
Input example #1
9
2 2 4 2 3 2 1 2 4
Output example #1
1