svoid test_LCSortedPairIndex() {
  long pairs[] = toLongArray(shuffledIterator(ll(500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 5500)));
  LCSortedPairIndex index = new(pairs);
  for i over pairs:
    assertEqualsVerbose(i, index.get(pairs[i])];
  assertEquals(-1, index.get(777));
}