/in/foo.cc: In function 'void getprimes_2()':
/in/foo.cc:13:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   13 |                 for (int j=0;j<primes.size()&&primes[j]*i<=N;j++)
      |                              ~^~~~~~~~~~~~~~