Compilare: user.cpp: In function ‘int main()’: user.cpp:36:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int k=0;k<primes.size();++k) { ^ user.cpp:54:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<primes.size();++i) { ^ user.cpp:9:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("nummst.in","r",stdin); ^ user.cpp:10:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("nummst.out","w",stdout); ^ user.cpp:11:16: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&N); ^