private static int SPRToInt(String str) {
		if (str.equals("POP")) {
			return 0x18;
		} else if (str.equals("PEEK")) {
			return 0x19;
		} else if (str.equals("PUSH")) {
			return 0x1a;
		} else if (str.equals("SP")) {
			return 0x1b;
		} else if (str.equals("PC")) {
			return 0x1c;
		} else if (str.equals("O")) {
			return 0x1d;
		} else {
			throw new IllegalArgumentException(
					"No such special-purpose register: " + str);
		}
	}