/in/foo.cc: In function 'int main()':
/in/foo.cc:26:2: warning: label 'start' defined but not used [-Wunused-label]
  start:
  ^~~~~
/in/foo.cc:32:2: warning: label 'blocking' defined but not used [-Wunused-label]
  blocking:
  ^~~~~~~~
/in/foo.cc: In function 'int bfs()':
/in/foo.cc:66:7: warning: suggest explicit braces to avoid ambiguous 'else' [-Wdangling-else]
     if(!check[j])
       ^