Squares#145
Given the lengths of segments, determine the maximum number of squares that can be formed from them. Each side of a square must be formed by exactly one segment, and each segment can be used for at most one square side. Only four segments of equal length can be used together to form a square.
The first line contains one integer (1 \leq n \leq 10^6) — the number of segments. The second line contains positive integers, each not exceeding , representing the lengths of the segments.
Print one integer — the maximum number of squares that can be formed from the given segments.
Example 1