Kent-buggen

import java.util.HashMap;
import java.util.Scanner;

public class KentBuggen {

	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int nameCount = Integer.valueOf(scan.nextLine());
		HashMap<String, Boolean> checkDB = new HashMap<String, Boolean>();
		int dubs = 0;
		for (int i = 0; i < nameCount; i++) {
			String name = scan.nextLine();
			if (!checkDB.containsKey(name)) {
				checkDB.put(name, false);
			} else if (!checkDB.get(name)) {
				dubs++;
				checkDB.put(name, true);
			}
		}
		System.out.println(dubs);
		scan.close();
	}
}