image.png

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();
        }
        int b = sc.nextInt();
        for(int i = 0; i < n; i++){
            if(b==a[i]){
                System.out.println(i+1);
                return;
            }
        }
        System.out.println(-1);
    }
}