/in/foo.cc: In function 'void dfs(int, int)':
/in/foo.cc:17:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < G[u].size(); i++) {
                     ~~^~~~~~~~~~~~~
/in/foo.cc: In function 'void solve(int)':
/in/foo.cc:31:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < cir.size(); i++) dfs(cir[i], cir[i]); // 子树DP
                     ~~^~~~~~~~~~~~
/in/foo.cc:36:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 1; i < cir.size(); i++) {
                     ~~^~~~~~~~~~~~
/in/foo.cc:44:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 1; i < cir.size(); i++) {
                     ~~^~~~~~~~~~~~