Compilare: user.cpp: In function ‘long long int STN(std::string)’: user.cpp:22:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < number.length(); i++){ ^ user.cpp: In function ‘int main()’: user.cpp:33:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("fetite.in", "r", stdin); ^ user.cpp:34:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("fetite.out", "w", stdout); ^ user.cpp:36:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &N); ^