Compilare: user.cpp: In function ‘long long int factor(const string&, int&)’: user.cpp:31:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (idx < s.size() && '0' <= s[idx] && s[idx] <= '9') { ~~~~^~~~~~~~~~ user.cpp: In function ‘int main()’: user.cpp:40:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("evaluare.in", "r", stdin); ^ user.cpp:41:41: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("evaluare.out", "w", stdout); ^