nor.cpp: In function 'void read()': nor.cpp:19: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result nor.cpp:23: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result nor.cpp: In function 'int BFS(int)': nor.cpp:32: warning: comparison between signed and unsigned integer expressions nor.cpp: In function 'int main()': nor.cpp:65: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result nor.cpp:65: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result