Compilare: main.cpp: In function 'int main()': main.cpp:67:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = index; i < primes.size(); i++){ ~~^~~~~~~~~~~~~~~ main.cpp:9:34: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("tygyn.in","r",stdin); ^ main.cpp:11:36: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("tygyn.out","w",stdout); ^