Compilare: user.cpp: In function ‘void back(int)’: user.cpp:46:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(k == Prime.size() - 1) ^ user.cpp: In function ‘int main()’: user.cpp:78:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < Sol.size(); i++) ^ user.cpp:68:41: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("armonica.out", "w", stdout); ^