import java.net.*;   //for class InetAddress in lines 12-13

class Class {
	static public void main(String argv[]) {
		if (argv.length != 1) {
			System.err.println(
				"Class: argument must be a dotted IPv4 address");
			System.exit(1);
		}

		try {
			final InetAddress ip = InetAddress.getByName(argv[0]);
			final byte[] b = ip.getAddress();   //array of 4 bytes
			final byte i = b[0];                //the high order byte

			char c;        //IPv4 address class: A, B, C, D, or E

			if ((i & 1 << 7) == 0) {
				c = 'A';   //Bit 31 is 0 (includes loopback address).
			} else if ((i & 1 << 6) == 0) {
				c = 'B';   //Bit 31 is 1, bit 30 is 0.
			} else if ((i & 1 << 5) == 0) {
				c = 'C';   //Bit 31 is 1, bit 30 is 1, bit 29 is 0.
			} else if ((i & 1 << 4) == 0) {
				c = 'D';   //Bit 31 is 1, bit 30 is 1, 29 is 1, 28 is 0.
			} else {
				c = 'E';   //Bit 31 is 1, bit 30 is 1, 29 is 1, 28 is 1.
			}

			System.out.println(argv[0] + " is a class " + c
				+ " IPv4 address.");
			System.exit(0);
		}

		catch (Exception e) {   //may be thrown by getByName in line 12
			System.err.println("argument " + argv[0]
				+ " must be a dotted IPv4 address");
			System.exit(2);
		}
	}
}