/in/foo.cc: In function 'void init(int, int)':
/in/foo.cc:39:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < G[v].size(); i++) {
                     ~~^~~~~~~~~~~~~
/in/foo.cc: In function 'void dfs(int)':
/in/foo.cc:47:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < G[v].size(); i++) {
                     ~~^~~~~~~~~~~~~