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 $n(1\le n\le 10^6)$. 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.

Examples