private String AddByBit(String str1, String str2) 
	{
		StringBuffer sumBuffer = new StringBuffer();
		for(int i = 0; i < str1.length(); ++i)
		{
			if(str1.charAt(i) == str2.charAt(i))
			{
				sumBuffer.append("0");
			}
			else
			{
				sumBuffer.append("1");
			}
		}
		return sumBuffer.toString();
	}