/in/foo.cc: In function 'int main()':
/in/foo.cc:13:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  while(s.find(a)!=-1)
        ~~~~~~~~~^~~~
/in/foo.cc:9:6: warning: unused variable 'slen' [-Wunused-variable]
  int slen=s.size();
      ^~~~
/in/foo.cc:11:6: warning: unused variable 'blen' [-Wunused-variable]
  int blen=b.size();
      ^~~~
/in/foo.cc:12:6: warning: unused variable 'spos' [-Wunused-variable]
  int spos=0;
      ^~~~