Compilare: user.cpp: In function ‘void dfs(std::stack<int>, std::__cxx11::list<int>, std::vector<int>, std::vector<std::vector<int> >)’: user.cpp:17:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<arcs[x].size(); ++i) ~^~~~~~~~~~~~~~~ user.cpp: In function ‘int main()’: user.cpp:28:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("sortaret.in", "r", stdin); ^ user.cpp:29:41: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("sortaret.out", "w", stdout); ^ user.cpp:32:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &n, &m); ^ user.cpp:41:30: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &x, &y); ^