foo.cc: In function 'int main()':
foo.cc:106:40: error: missing template arguments before '(' token
     if (ans1 == f[root][0]) ans2 = plus(ans2, d[root][0]);
                                        ^
foo.cc:107:40: error: missing template arguments before '(' token
     if (ans1 == f[root][1]) ans2 = plus(ans2, d[root][1]);
                                        ^

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。