grad.cpp: In function 'int main()': grad.cpp:8: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result grad.cpp:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result grad.cpp:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result grad.cpp:11: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result grad.cpp:12: warning: ignoring return value of 'char* gets(char*)', declared with attribute warn_unused_result /tmp/ccdak4YY.o: In function `main': grad.cpp:(.text+0x7e): warning: the `gets' function is dangerous and should not be used.