  In the 3SUM-Indexing problem the goal is to preprocess two lists of elements
from $U$, $A=(a_1,a_2,\ldots,a_n)$ and $B=(b_1,b_2,...,b_n)$, such that given
an element $c\in U$ one can quickly determine whether there exists a pair
$(a,b)\in A \times B$ where $a+b=c$. Goldstein et al.~[WADS'2017] conjectured
that there is no algorithm for 3SUM-Indexing which uses $n^{2-\Omega(1)}$ space
and $n^{1-\Omega(1)}$ query time.
  We show that the conjecture is false by reducing the 3SUM-Indexing problem to
the problem of inverting functions, and then applying an algorithm of Fiat and
Naor [SICOMP'1999] for inverting functions.
