foo.cc: In function ‘int main()’:
foo.cc:23:22: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::size_t’ {aka ‘long unsigned int’} [-Wsign-compare]
   23 |         for(int i=0;i<b1.size();i++)
      |                     ~^~~~~~~~~~
foo.cc:28:22: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::size_t’ {aka ‘long unsigned int’} [-Wsign-compare]
   28 |         for(int i=0;i<b2.size();i++)
      |                     ~^~~~~~~~~~
foo.cc:15:17: warning: iteration 1024 invokes undefined behavior [-Waggressive-loop-optimizations]
   15 |         num[i+1]=num[i]*2%mod;
      |         ~~~~~~~~^~~~~~~~~~~~~
foo.cc:14:18: note: within this loop
   14 |     for(int i=0;i<=1024;i++)
      |                 ~^~~~~~