virus.cpp: In function 'void read()': virus.cpp:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result virus.cpp:11: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result virus.cpp: In function 'void make_prefix()': virus.cpp:16: warning: unused variable 'i' virus.cpp: In function 'void make_match()': virus.cpp:27: warning: unused variable 'i' virus.cpp: In function 'void answer()': virus.cpp:51: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result virus.cpp: In function 'int main()': virus.cpp:58: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result virus.cpp:59: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result