n = int(input())
li = list(map(int,input().split()))
m = int(input())
if m in li:
        print(li.index(m)+1)
else:
        print(-1)

/**************************************************************
	Problem: 1154
	User: admin
	Language: Python
	Result: Accepted
	Time:202 ms
	Memory:34244 kb
****************************************************************/