Compilare: user.cpp:2:6: warning: ISO C++ forbids declaration of ‘main’ with no type [-Wreturn-type] main(){std::ifstream f ("aria.in");freopen("aria.out","w",stdout); ^ user.cpp: In function ‘int main()’: user.cpp:2:66: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] main(){std::ifstream f ("aria.in");freopen("aria.out","w",stdout); ^