prime1.cpp: In function 'int main()': prime1.cpp:52: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result prime1.cpp:53: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result prime1.cpp:54: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result prime1.cpp:57: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result prime1.cpp:58: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result