foo.cc: In function 'int main()':
foo.cc:6:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
    6 |  freopen("a.txt","r",stdin);
      |  ~~~~~~~^~~~~~~~~~~~~~~~~~~
foo.cc:7:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
    7 |  freopen("b.txt","w",stdout);
      |  ~~~~~~~^~~~~~~~~~~~~~~~~~~~

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Found 10 testcases.
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