print((function (f)
	local a,h,r,n,x={},{},0,f(),f()
	for i=1,n do a[i]=f() end
	for i=1,n do if h[a[i]]==nil then h[a[i]]=0 end h[a[i]]=h[a[i]]+1 end
	for i=1,n do if h[x-a[i]]~=nil then r=r+h[x-a[i]] end end
	return r
end)((function (M)
	M.cdef 'int scanf(const char *, ...);'
	local C,c = M.C,M.new("int[1]")
	return function () C.scanf("%d",c) return c[0] end
end)(require'ffi')))