/in/foo.cc:33:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
 main() { 
      ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:39:15: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   int mid = l + r >> 1; 
             ~~^~~
/in/foo.cc:43:22: warning: 'ans' may be used uninitialized in this function [-Wmaybe-uninitialized]
  printf("%lld\n",ans);
                      ^