private static BigInteger calculateSom(BigInteger x) {

		if(x.compareTo(new BigInteger("10")) < 0) {
			return x;
		}
		else {
			BigInteger y = x.mod(new BigInteger("10"));
			BigInteger z = x.divide(new BigInteger("10"));
			x = y.add(calculateSom(z));
		}
		return x;
	}