/in/foo.cc: In function 'void res()':
/in/foo.cc:11:30: warning: iteration 1000003 invokes undefined behavior [-Waggressive-loop-optimizations]
   11 |                 if (Isprime[i])
      |                     ~~~~~~~~~^
/in/foo.cc:9:23: note: within this loop
    9 |         for (int i=2;i<=N;i++)
      |                      ~^~~