perspic.cpp: In function 'int main()': perspic.cpp:23: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result perspic.cpp:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result perspic.cpp:27: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result perspic.cpp:36: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result perspic.cpp:37: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result perspic.cpp:39: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result perspic.cpp:41: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result perspic.cpp:45: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result perspic.cpp:49: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result