123.cpp: In function 'int main()': 123.cpp:15: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result 123.cpp:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result 123.cpp:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result 123.cpp:20: warning: ignoring return value of 'char* gets(char*)', declared with attribute warn_unused_result /tmp/cc9tLEkG.o: In function `main': 123.cpp:(.text+0x7a): warning: the `gets' function is dangerous and should not be used.