sl.cpp: In function 'void read()': sl.cpp:25: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result sl.cpp:27: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result sl.cpp:30: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result sl.cpp:47: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result sl.cpp:50: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result sl.cpp: In function 'void write()': sl.cpp:81: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result