for _ in range(int(input())):
	a=bin(int(input()))[2:]
	c=0
	ans=0
	for i in reversed(range(len(a))):
	    if a[i]=='1':
	        c+=1
	    if c==1:
	        ans+=pow(2,len(a)-1-i)
	    if c==2:
	        print(ans)
	        break 
	else:
	    print(-1)