/in/foo.cc: In function 'int main()':
/in/foo.cc:33:24: warning: iteration 100005 invokes undefined behavior [-Waggressive-loop-optimizations]
             ans+=b[j][i]*c[j][i];
                  ~~~~~~^
/in/foo.cc:31:20: note: within this loop
     for (int i=0; i<=MAXN; i++) 
                   ~^~~~~~