func main()
	var n: int :: cui@inputInt()
	
	var a: []int :: #[n]int
	for i(0, n - 1)
		do a[i] :: cui@inputInt()
	end for
	
	do a.sort()
	
	var ans: int :: 0
	for i(0, n - 2)
		if(a[i] = a[i + 1])
			do i :+ 1
			do ans :+ 1
		end if
	end for
	do cui@print("\{ans}\n")
end func