trading.cpp: In function 'int main()':
trading.cpp:4:48: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
4 | #define file(s) if (fopen(s".in", "r")) freopen(s".in", "r", stdin), freopen(s".out", "w", stdout)
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~
trading.cpp:42:2: note: in expansion of macro 'file'
42 | file("trading");
| ^~~~
trading.cpp:4:77: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
4 | #define file(s) if (fopen(s".in", "r")) freopen(s".in", "r", stdin), freopen(s".out", "w", stdout)
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
trading.cpp:42:2: note: in expansion of macro 'file'
42 | file("trading");
| ^~~~