ab.cpp: In function 'int main()': ab.cpp:8: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result ab.cpp:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result ab.cpp:10: warning: ignoring return value of 'char* gets(char*)', declared with attribute warn_unused_result /tmp/cclkd6CG.o: In function `main': ab.cpp:(.text+0x56): warning: the `gets' function is dangerous and should not be used.