public static int[] Sort(int[] input, int k) {
		if (input == null || k < 0) {
			return null;
		}
		int[] count = new int[k];
		for (int i = 0; i < input.length; i++) {// O(N)
			count[input[i]] += 1;
		}
		for (int i = 1; i < k; i++) {// O(K)
			count[i] += count[i - 1];
		}
		int[] result = new int[input.length];
		for (int i = input.length - 1; i >= 0; i--) {// O(N)
			result[count[input[i]] - 1] = input[i];
			count[input[i]] -= 1;
		}
		return result;
	}