/in/foo.cc: In function 'void dfs(int, int)':
/in/foo.cc:16:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<a[rt].size();i++)
              ~^~~~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:82:36: warning: zero-length gnu_printf format string [-Wformat-zero-length]
  printf("%d",num[i]),i==n?printf(""):printf(" ");
                                    ^