while(1):
    try:
        n=int(input())
        s=list(map(int,input().split()))
        m=int(input())
        l=len(s)
        count=0
        for i in range(l):
            if(s[i]==m):
                print(i)
                count+=1
        if(count==0):
            print("-1")
    except:
        break