foo.cc: In function 'int main()':
foo.cc:76:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   76 |     freopen("set.in","r",stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~
foo.cc:77:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   77 |  freopen("set.out","w",stdout);
      |  ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

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