/in/foo.cc: In function 'int main()':
/in/foo.cc:11:24: warning: iteration 1000008 invokes undefined behavior [-Waggressive-loop-optimizations]
   11 |                 if (b[i] == 0)
      |                     ~~~^
/in/foo.cc:10:27: note: within this loop
   10 |         for (int i = 2; i <= N; i ++) {
      |                         ~~^~~~