optim.cpp: In function 'int main()': optim.cpp:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result optim.cpp:13: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result optim.cpp:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result optim.cpp:16: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result