import java.util.*;

public class VowelCheck {

	public static void main(String[] args) {
		String s;
		char letter;
		Scanner input = new Scanner(System.in);
		
		System.out.print("Enter a letter: ");
		s = input.next();
		if (s.length() > 1) {
			throw new IllegalStateException("Input must be single letter.");
		}
		
		if (isVowel(s.charAt(0))) {
			System.out.println("Letter is a vowel");
		}
		else {
			System.out.println("Letter is not a vowel");
		}

	}
	
	//----------------------------------------------
//  Precondition:  letter is an uppercase or
//  lowercase letter (in the range 'A' ... 'Z' or 'a' ... 'z') .
//  Postcondition:  The value returned by the
//  method is true if letter is a vowel;
//  otherwise the value returned by the method is
//  false. 
	public static boolean isVowel(char c) {
		String vowels = "aeiouAEIOU";
				
		return (vowels.indexOf(c) >= 0); 
	}

}