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I use "new"(C++) to allocate memory to store the input data. And I use a string buffer with size 65536 when reading a formula. When I have read all data, I store them and use "top-down DP" method to count each fields. But I get a Runtime Error(SIGSEGV). How should I do to solve this problem? Thanks ...

Should I sort the solution strings?
And is there any illegal position of piece 'a' in the input?
Thanks for your answer.