Compilare: user.cpp: In function ‘void dfs(int)’: user.cpp:31:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (x==i) nr++; ^ user.cpp: In function ‘int main()’: user.cpp:50:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=0;i<sol.size();i++) { ^ user.cpp:52:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j=0;j<sol[i].size();j++) a.insert(sol[i][j].first),a.insert(sol[i][j].second); ^ user.cpp:40:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("biconex.in","r",stdin); ^ user.cpp:41:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("biconex.out","w",stdout); ^ user.cpp:42:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d",&n,&m); ^ user.cpp:44:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d",&x,&y); ^