/in/foo.cc: In function 'int main()':
/in/foo.cc:20:24: warning: iteration 49998 invokes undefined behavior [-Waggressive-loop-optimizations]
   20 |                 if (a[i] == 0) {
      |                     ~~~^
/in/foo.cc:19:27: note: within this loop
   19 |         for (int i = 2; i <= N; i ++) {
      |                         ~~^~~~