Compilare: user.cpp: In function ‘int pairup(int)’: user.cpp:20:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0;i<G[nod].size();i++) ^ user.cpp:28:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i =0;i< G[nod].size();i++) ^ user.cpp: In function ‘int main()’: user.cpp:54:11: warning: suggest explicit braces to avoid ambiguous ‘else’ [-Wparentheses] if(!l[i]) ^ user.cpp:42:31: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen(iname, "r", stdin); ^ user.cpp:43:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen(oname, "w", stdout); ^ user.cpp:45:29: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d",&n,&m,&e); ^ user.cpp:48:28: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&a,&b); ^