/in/foo.cc: In function 'int main()':
/in/foo.cc:28:27: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   28 |                 if(j!=v[i]&&v[j]==j || 1LL*v[i]*v[i]*v[i]==i)n--;
      |                    ~~~~~~~^~~~~~~~~
/in/foo.cc: In function 'void init()':
/in/foo.cc:9:23: warning: iteration 5200003 invokes undefined behavior [-Waggressive-loop-optimizations]
    9 |                 if(v[i]==0)
      |                    ~~~^
/in/foo.cc:7:22: note: within this loop
    7 |         for(int i=2;i<=M;i++)
      |                     ~^~~