foo.cc: In function ‘int main()’:
foo.cc:10:23: warning: iteration 999998 invokes undefined behavior [-Waggressive-loop-optimizations]
   10 |                 num[i]=((num[i-1]%p)*(i%p))%p;;
      |                       ^
foo.cc:9:23: note: within this loop
    9 |         for (int i=2;i<=1000000;i++)
      |                      ~^~~~~~~~~