sub.cpp: In function 'int main()': sub.cpp:52: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result sub.cpp:53: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result sub.cpp:57: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result sub.cpp:59: warning: ignoring return value of 'char* gets(char*)', declared with attribute warn_unused_result sub.cpp:65: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result sub.cpp:67: warning: ignoring return value of 'char* gets(char*)', declared with attribute warn_unused_result /tmp/ccotO4o5.o: In function `main': sub.cpp:(.text+0x1c6): warning: the `gets' function is dangerous and should not be used.