char[] uniqueChars(char[] s) {
		int tail=1;
		for (int i=1,j=0;i<s.length;++i) {
			for (j=0;j<tail;++j) 
				if (s[j]==s[i]) break;
			if (j==tail) s[tail++]=s[i];				
		}
		return Arrays.copyOf(s, tail);
	}