Compilare: user.cpp: In member function ‘HN& HN::operator+(const HN&)’: user.cpp:38:12: warning: reference to local variable ‘ans’ returned [-Wreturn-local-addr] HN ans; ^ user.cpp: In member function ‘HN& HN::operator-(const HN&)’: user.cpp:52:12: warning: reference to local variable ‘ans’ returned [-Wreturn-local-addr] HN ans; ^ user.cpp: In function ‘int main()’: user.cpp:105:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("indep.in", "r", stdin); ^ user.cpp:106:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("indep.out", "w", stdout); ^ user.cpp:108:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^ user.cpp:112:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &a[i]); ^