foo.cc: In function 'int main()':
foo.cc:7:9: warning: unused variable 'bs' [-Wunused-variable]
  int n, bs=0, cnt;
         ^~
foo.cc:19:6: warning: 'cnt' may be used uninitialized in this function [-Wmaybe-uninitialized]
  cout<<cnt;
  ~~~~^~~~~