strange_device.cpp: In function 'void setIn(std::string)':
strange_device.cpp:7:31: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
    7 | void setIn(string s) { freopen(s.c_str(), "r", stdin); }
      |                        ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
strange_device.cpp: In function 'void setOut(std::string)':
strange_device.cpp:8:32: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
    8 | void setOut(string s) { freopen(s.c_str(), "w", stdout); }
      |                         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
strange_device.cpp: In function 'int main()':
strange_device.cpp:4:52: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
    4 | #define file if (fopen("input.txt", "r")) { freopen("input.txt", "r", stdin); freopen("output.txt", "w", stdout); }
      |                                             ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
strange_device.cpp:46:5: note: in expansion of macro 'file'
   46 |     file;
      |     ^~~~
strange_device.cpp:4:86: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
    4 | #define file if (fopen("input.txt", "r")) { freopen("input.txt", "r", stdin); freopen("output.txt", "w", stdout); }
      |                                                                               ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
strange_device.cpp:46:5: note: in expansion of macro 'file'
   46 |     file;
      |     ^~~~