#include<stdio.h>
#include<malloc.h>

int main()
{
	int n;
	scanf("%d", &n);

	int *ar = (int *)malloc(sizeof(int)*n);
	if (ar == NULL)
		return -1;

	for (int i = 0; i < n; i++)
		scanf("%d", &ar[i]);

	int x;
	scanf("%d", &x);
	int found = -1;

	for (int i = 0; i < n; i++)
	{
		if (ar[i] == x)
		{
			printf("%d", i);
			found = i;
			break;
		}
	}
	if (found == -1)
		printf("-1");

	free(ar);
	return 0;
}