!7

p {
  assertEqualsVerbose("A", charactersAppearingExactlyOnceInEachString(ll("bggkA"));
  assertEqualsVerbose("A", charactersAppearingExactlyOnceInEachString(ll("bggkA", "Abbl"));
  assertEqualsVerbose("AB", sortedString(charactersAppearingExactlyOnceInEachString(ll("bggkAB", "BAbbl"))));
}