/in/foo.cc: In function 'int main()':
/in/foo.cc:38:14: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
         mid=l+r>>1;
             ~^~
/in/foo.cc:42:21: error: 'prntf' was not declared in this scope
     prntf("%lld",ans);
                     ^