/in/foo.cc: In function 'void getprimes2(int)':
/in/foo.cc:13:30: 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()&&i*primes[j]<=n;j++)
      |                             ~^~~~~~~~~~~~~~