Compilare: user.cpp: In function ‘void df(int)’: user.cpp:16:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<a[k].size();i++) ^ user.cpp: In function ‘int main()’: user.cpp:25:23: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%d%d",&n,&m); ^ user.cpp:28:23: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%d%d",&x,&y); ^