OJ Board

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.