text: // Simple Fun #352: Reagent Formula
  
  function isValid(formula) {
      //coding and coding..
      const rule1 = !(formula.includes(1) && formula.includes(2));
      const rule2 = !(formula.includes(3) && formula.includes(4));
      const rule3 = formula.includes(5) === formula.includes(6);
      const rule4 = formula.includes(7) || formula.includes(8);
      return rule1 && rule2 && rule3 && rule4;
  }