private static void fillEssentialPrime(int combinationLength) {
        ArrayList<String> combinationEssential = new ArrayList<String>();
        for (int i = 0; i < combinationLength; i++) {
            System.out.println(combination[i]);
            combinationEssential.add(combination[i]);
        }
        for (int i = 0; i < essentialPrimeImplicantsContainingOne.size(); i++)
            System.out.println(essentialPrimeImplicantsContainingOne.get(i));
        System.out.println();
        String expression = findExpression(essentialPrimeImplicantsContainingOne);
        if(!expression.equals(""))
            expression+= " + ";
        expression += findExpression(combinationEssential);
        System.out.println(expression);
        System.out.println();
    }