/in/foo.cc: In function 'int build(int, int)':
/in/foo.cc:82:11: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  int mid=l+r>>1;
          ~^~
/in/foo.cc: In function 'int main()':
/in/foo.cc:141:14: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
     int mid=l+r>>1;
             ~^~