import java.util.Scanner;
//找x
public class Main_301 {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
while (scanner.hasNext()) {
int num = scanner.nextInt();
int[] arr = new int[num];
for (int i = 0; i < num; i++) {
arr[i] = scanner.nextInt();
}
int find = scanner.nextInt();
for (int i = 0; i < num; i++) {
if (find == arr[i]) {
System.out.println(i);
break;
}
if (i == num - 1) {
System.out.println(-1);
}
}
}
}
}
