Compilare: user.cpp: In function ‘void df(long int, long int)’: user.cpp:13:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=0;i<m[x].size();++i) { ^ user.cpp:17:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j=0;j<=st.size()-1;++j) ^ user.cpp: In function ‘int main()’: user.cpp:27:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("arbore3.in","r",stdin); ^ 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 ("arbore3.out","w",stdout); ^ user.cpp:29:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%ld%ld",&n,&s); ^ user.cpp:31:30: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%ld%ld",&x,&y); ^