/in/foo.cc: In function 'void solve()':
/in/foo.cc:22:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<ss.length();i++) {
              ~^~~~~~~~~~~~
/in/foo.cc:37:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<ss.length();i++) {
              ~^~~~~~~~~~~~
/in/foo.cc:21:6: warning: unused variable 'st' [-Wunused-variable]
  int st=0; bool flag=true;
      ^~