private static BigInteger recSum(BigInteger val, BigInteger moddiv, BigInteger result){
    if(moddiv.compareTo(val) == 1){
        return result;
    }else{
        val = val.mod(moddiv);
        moddiv = moddiv.multiply(BigInteger.valueOf(10));
        result = result.add(recSum(val, moddiv, result));
    }
}