replace.cpp: In function 'int main()': replace.cpp:11: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result replace.cpp:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result replace.cpp:15: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result replace.cpp:17: warning: ignoring return value of 'char* gets(char*)', declared with attribute warn_unused_result replace.cpp:18: warning: ignoring return value of 'char* gets(char*)', declared with attribute warn_unused_result replace.cpp:22: warning: ignoring return value of 'char* gets(char*)', declared with attribute warn_unused_result /tmp/ccq48PUY.o: In function `main': replace.cpp:(.text+0x89): warning: the `gets' function is dangerous and should not be used.