/in/foo.cc: In function 'int main()':
/in/foo.cc:11:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   11 |                 for(int j=0; j<primes.size()&&i*primes[j]<=N; j++) {
      |                              ~^~~~~~~~~~~~~~