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. \InputFile 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 $100$. \OutputFile Print the maximum number of squares that can be constructed from the given segments.