How to play this grupetto?

[mariojar]

In Schumann's "Rememberances" there is a second grupetto between a# and c#. How to play this grupetto taking into consideration that the lower note has double sharp and this piece is in A major? b(upper note)-a#(main note)-a#(g# with double sharp)-a#(main note)-c# sounds odd. b-a#-a-a#-c# seems to be better but in that case the lower note is g, not g#. 
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