include

using namespace std; int A[101];

int main() {

int n, a, num = -2;
scanf("%d", &n);

for (int i = 0; i < n; i++) {

	scanf("%d", &A[i]);
}

scanf("%d", &a);

for (int i = 0; i < n; i++) {

	if (A[i] == a) {
		num = i;
		break;
	}
}

printf("%d", num+1);
return 0;

}