Compilare: user.cpp: In function ‘void erato(std::vector<int>&)’: user.cpp:9:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(unsigned i = 2; i < a; i++) ^ user.cpp:13:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(unsigned j = i * i; j < a; j += i) ^ user.cpp: In function ‘void bt(long long int&, std::vector<int>&, std::vector<long long int>&, int, long long int, int)’: user.cpp:30:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(myV.size() == k) ^ user.cpp:38:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i < myP.size()) ^