/in/foo.cc: In function 'int main()':
/in/foo.cc:46:21: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
         if(x=a||flag)x=b;
                     ^
/in/foo.cc:38:36: warning: iteration 6005 invokes undefined behavior [-Waggressive-loop-optimizations]
  for(int i=0;i<=M;i++)t[i].l=t[i].r=0;
                              ~~~~~~^~
/in/foo.cc:38:15: note: within this loop
  for(int i=0;i<=M;i++)t[i].l=t[i].r=0;
              ~^~~