foo.cc: In function 'int main()':
foo.cc:9:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
  freopen("Input/in4.in","r",stdin);
  ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:10:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
  freopen("Output/out4.out","w",stdout);
  ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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