onu2.cpp: In function 'int main()': onu2.cpp:72: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result onu2.cpp:73: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result onu2.cpp:74: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result onu2.cpp:77: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result