Upvote:3
As you wrote yourself in your comments already, you need to have an additional visa. One choice is that you get another visa for the second entry, or you organize for a multiple entry visa.
The multiple entry visa however will likely only be granted if you have traveled to Europe several times before that.
Since your two entries are one month apart from each other, there should be no issue for them giving you an additional visa, since the minimum period for a visa is three months before the trip.