/in/foo.cc: In function 'int main()':
/in/foo.cc:47:13: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
    int mid=l+r>>1;
            ~^~
/in/foo.cc:53:21: warning: 'ans' may be used uninitialized in this function [-Wmaybe-uninitialized]
   printf("%d\n",ans);
                     ^