Q=int(input())
for _ in range(Q):
	N,M=map(int,input().split())
	left=-1
	right=N
	while right-left>1:
		mid=(right+left)//2
		a=N-4*mid
		b=(a//2)*4+M-2*mid
		if a>=0 and b>=0:
			left=mid
		else:
			right=mid
	print(max(0,left*3))