public String get_plain_with_blank(String s)
	{
		String low_s=s.toLowerCase();
		StringBuilder b=new StringBuilder();
		for(char a:low_s.toCharArray())
		{
			if(a==' ' || (a>='a' && a<='z'))
			{
				b.append(a);
			}
		}
		return b.toString();
	}