/in/foo.cc: In function 'void R(int&)':
/in/foo.cc:12:10: warning: suggest parentheses around '+' inside '<<' [-Wparentheses]
   v = (v + (v << 2) << 1) + (ch^'0');
        ~~^~~~~~~~~~
/in/foo.cc: In function 'void dfs(int)':
/in/foo.cc:41:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i <  q[x].size(); ++i) {
                  ~~^~~~~~~~~~~~~~
/in/foo.cc:32:8: warning: unused variable 'p' [-Wunused-variable]
  node *p;
        ^