private String getLeftStringResult(String step, int pos, char value) {
		String result = "";
		pos--; // the initial position is already taken care of
		for (; pos >= 0; pos--) {
			if (step.charAt(pos) != '0' && step.charAt(pos) != '1') {
				break;
			}
			result += value;
		}
		return result;
	}