/in/foo.cc: In function 'll Bin_search()':
/in/foo.cc:39:16: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
     ll mid = l + r >> 1;
              ~~^~~
/in/foo.cc:43:10: warning: 'ans' may be used uninitialized in this function [-Wmaybe-uninitialized]
   return ans;
          ^~~