virus.cpp: In function 'int main()': virus.cpp:21: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result virus.cpp:22: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result virus.cpp:23: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result virus.cpp:24: warning: ignoring return value of 'char* gets(char*)', declared with attribute warn_unused_result virus.cpp:25: warning: ignoring return value of 'char* gets(char*)', declared with attribute warn_unused_result virus.cpp:39: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result virus.cpp:40: warning: ignoring return value of 'char* gets(char*)', declared with attribute warn_unused_result virus.cpp:41: warning: ignoring return value of 'char* gets(char*)', declared with attribute warn_unused_result /tmp/ccvpjM9W.o: In function `main': virus.cpp:(.text+0x81): warning: the `gets' function is dangerous and should not be used.