Compilare: user.cpp: In function ‘void back(int, int)’: user.cpp:20:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<v[p].s();++i)++w[v[p][i]]; ^ user.cpp:22:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<v[p].s();++i)--w[v[p][i]]; ^ user.cpp: In function ‘int main()’: user.cpp:28:22: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%d",&t); ^ user.cpp:33:31: 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:41:35: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%d%d",&x,&y); ^