Compilare: user.cpp: In function ‘int main()’: user.cpp:32:34: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f1,"%d%d%d%d",&n,&m,&x,&y); ^ user.cpp:33:44: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] for (i=1;i<=m;i++) {fscanf(f1,"%d%d",&u,&v);a[u].push_back(v);a[v].push_back(u);} ^