/in/foo.cc: In function 'void dp(int)':
/in/foo.cc:22:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(re int i=0;i<son[k].size();i++){
                 ~^~~~~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:55:6: warning: unused variable 'ans' [-Wunused-variable]
  int ans=-1;
      ^~~