/in/foo.cc: In function 'int main()':
/in/foo.cc:30:8: warning: iteration 300004 invokes undefined behavior [-Waggressive-loop-optimizations]
   f[i] = i;
   ~~~~~^~~
/in/foo.cc:29:20: note: within this loop
  for (int i = 1; i <= Maxn; i++) {
                  ~~^~~~~~~