Singer Demi Lovato will perform June 21 at Roosevelt Field in Garden City as part of the grand opening of Microsoft's newest retail store, with free tickets available to those who get in line early for the daylong festivities.

An opening ceremony begins at 10:30 a.m., followed by the store's opening at 11 a.m. The first 200 attendees in line will receive two tickets to the 7 p.m. concert and one ticket for access for one person to a preshow meet-and-greet with Lovato.

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The next 1,500 people in line will each receive two tickets to the show. The concert will take place in the mall's northeast parking lot, a Microsoft spokeswoman said. Gates open at 5 p.m.

The new 3,775-square-foot store will be staffed by 41 employees and will sell a range of Microsoft products, including Windows 8 PCs, Surface tablets and Xbox One gaming consoles.

The store is Microsoft's fourth full-line retail location in New York and second on Long Island. Microsoft opened a store at Walt Whitman Shops in Huntington Station in 2012. The company also operates two smaller specialty stores in the state, including one at Roosevelt Field. That store will close June 20, the spokeswoman said.

Those waiting for tickets will be permitted to line up June 20 beginning at 10 p.m. outside the northeast parking garage near Bloomingdale's.

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For more ticket and concert information, visit .