public static String readSeatNumbers() {
		boolean tryAgain;
		
		do {
			tryAgain = false;
			str = scan.nextLine();
			
			for(String s: str.split(" ")) {
			
				if(s.length() < 2) {
					tryAgain = true;
				}
				else if(s.charAt(0) < 'A' && s.charAt(0) > 'Z') {
					tryAgain = true;
				}
				else {
					try {
						Integer.parseInt(s.substring(1, s.length()));
					} catch(NumberFormatException exception) {
						tryAgain = true;
					}
				}	
				
				if(tryAgain) {
					System.out.print("Seats No input is invalid! Try again: ");
					break;
				}
			}
			
		}while(tryAgain);
		
		return str;
	}