sumb.cpp: In function 'int main()': sumb.cpp:80: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result sumb.cpp:81: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result sumb.cpp:84: warning: ignoring return value of 'char* fgets(char*, int, FILE*)', declared with attribute warn_unused_result sumb.cpp:88: warning: ignoring return value of 'char* fgets(char*, int, FILE*)', declared with attribute warn_unused_result sumb.cpp:92: warning: ignoring return value of 'char* fgets(char*, int, FILE*)', declared with attribute warn_unused_result