Main.cc: In function ‘int main()’: Main.cc:62:7: error: binding reference of type ‘int&’ to ‘const int’ discards qualifiers dfs(N); ^ Main.cc:30:13: note: initializing argument 1 of ‘void dfs(int&)’ inline void dfs(int &u){ ^~~ Main.cc:56:7: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d ",&n); ~~~~~^~~~~~~~~~ Main.cc:58:7: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d" ,&a[i]); ~~~~~^~~~~~~~~~~~~