/in/foo.cc: In function 'int main()':
/in/foo.cc:16:14: warning: 'r' may be used uninitialized in this function [-Wmaybe-uninitialized]
   cout << b[r] - b[l - 1] << endl;
           ~~~^
/in/foo.cc:16:22: warning: 'l' may be used uninitialized in this function [-Wmaybe-uninitialized]
   cout << b[r] - b[l - 1] << endl;
                    ~~^~~