metrou.cpp: In function 'int main()': metrou.cpp:138: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result metrou.cpp:139: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result metrou.cpp:140: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result metrou.cpp:141: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result metrou.cpp:143: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result