sS ai_ruleOfThree_solver_4(S db, S input) {
  ret fixAOrAn(too_transformInput(input, too -> {
    // load rules
    too.addAll(lambdaMap ai_parseBasicLogicRule(tlft(db)));
  
    // turn words appearing in LHS and RHS into variables
    too.addTransformer(func(BasicLogicRule<S> r) {
      Set<S> suffixes = ai_suffixesFromSharedWordStarts(r);
      if (nempty(suffixes)) {
        print(+suffixes);
        // found suffixes. now transform all inputs & rules
        too.addTransformer(func(IInput<S> i) {
          TransformedInput(ai_splitOffWordSuffixes(suffixes, i!))
        });
        too.addTransformer(func(BasicLogicRule<S> r) {
          mapBasicLogicRule(r, s -> ai_splitOffWordSuffixes(suffixes, s))
        });
      }
      null;
    });
  
    // turn words appearing in LHS and RHS into variables
    too.addTransformer(f<BasicLogicRule<S>, O> ai_sharedPhrasesIntoDollarVars);
    
    // match input with rules
    too_flexMatchRulesToTransformInput(too);
  }));
}