/in/foo.cc: In function 'void dfs(const int&, const int&, const int&)':
/in/foo.cc:16:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < va[x].size(); i++) {
                     ~~^~~~~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:23:22: warning: format '%lld' expects argument of type 'long long int*', but argument 2 has type 'int*' [-Wformat=]
     scanf ("%lld", &n);
                      ^
/in/foo.cc:33:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int i = 0; i < va[x].size(); i++) {
                         ~~^~~~~~~~~~~~~~