wow.cpp: In function 'void read()': wow.cpp:32: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result wow.cpp:33: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result wow.cpp:36: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result wow.cpp:38: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result wow.cpp: In function 'void write()': wow.cpp:98: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result