Challenge: First Repeat

Lab Java Beginner 10 points

Read n numbers in order. Print the first number that appears for a second time (the one whose repeat comes earliest). If nothing repeats, print none.

Input

Line 1: n. Line 2: n whole numbers.

Output

The first repeated number, or none.

Example

Input

7
4 2 7 2 4 9 7

Output

Sample input available Sample output available

Editor

Java

Hints

Walk through the numbers with a HashSet of what you've seen.

seen.add(x) returns false when x was already there.

Solution explanation

One pass with O(1) set lookups: O(n). Read all n numbers before stopping, so no input is left over.

Show solution

import java.util.HashSet;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n];
        for (int i = 0; i < n; i++) a[i] = sc.nextInt();
        HashSet<Integer> seen = new HashSet<Integer>();
        for (int x : a) {
            if (!seen.add(x)) {
                System.out.println(x);
                return;
            }
        }
        System.out.println("none");
    }
}

Output

Answer