/in/foo.cc: In function 'int main()':
/in/foo.cc:21:17: warning: unused variable 'tmp' [-Wunused-variable]
   int ls = now, tmp; now ^= 1;
                 ^~~
/in/foo.cc:18:6: warning: unused variable 'len' [-Wunused-variable]
  int len = 1, now = 0;
      ^~~