T = int(input())
for _ in range(T):
    N,M = list(map(int,input().split()))

    def check(n):
        need = -(-n//3)
        wood = N - 4 * need
        if(wood < 0):return False
        stick = M + (wood // 2) * 4 - 2 * need
        return stick >= 0
        
    ok,ng = 0,10**12
    while(ng - ok > 1):
        mid = (ok+ng)//2
        if(check(mid)):
            ok = mid
        else:
            ng = mid
    print(ok)