sant1.cpp: In function 'void read()': sant1.cpp:20: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result sant1.cpp:21: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result sant1.cpp:24: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result sant1.cpp: In function 'void write()': sant1.cpp:53: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result