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import List data T=Char:=Int|N T T Int s(x:=_)=show x s(N a b _)='(':s a++s b++")" g(_:=a)=a g(N _ _ a)=a i[a]=a i(a:b:x)=t$N a b(g a+g b):x t=i.sortBy((.g).(compare.g)) main=interact$s.t.map(\x->x!!0:=length x).group.sort
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Program error: pattern match failure: i []