public static BigInteger convertoToRepresentationNumber(String representationString, char[] alfabet){
        Hashtable<Character,Integer> conversionFunction = new Hashtable<>();
        
        BigInteger base = BigInteger.valueOf(alfabet.length);
        BigInteger out = BigInteger.ZERO;        
        
        for(int i= 0; i < alfabet.length;i++){
            conversionFunction.put(alfabet[i], i);
        }
        
        char[] chars = representationString.toCharArray();
               
        for(int i= 0; i < chars.length ;i++ ){
            char representationStringCharacter = chars[i];
            BigInteger number = BigInteger.valueOf(conversionFunction.get(representationStringCharacter));
            out = out.add(number.multiply(base.pow(i)));
        }
        
        return out;
    }