public static String v(int[][] m) {
		String ans = "";
		if (s(m, -1, -1))
			return "OK";
		else {
			for (int i = 0; i < m.length; i++)
				for (int j = 0; j < m.length; j++)
					if (s(m, i, j))
						return "Change bit (" + (i + 1) + "," + (j + 1) + ")";
		}
		return "Corrupt";
	}