public static String[] removeDuplicate(String[][] sets){
		String[] result = new String[sets.length];
		Arrays.fill(result,"");
		for(int i = 0; i < sets.length; i++){
			//ASCII
			int[] hash = new int[128];
			for(int j = 0; j <sets[i].length; j++){
				hash[sets[i][j].charAt(0)]++;
			}
			for(int j = 0; j < hash.length; j++){
				if(hash[j] > 0){
					result[i] = result[i] + (char)j;
				}
			}
		}
		return result;
	}