Compilare: user.c: In function ‘main’: user.c:35:9: warning: statement with no effect [-Wunused-value] for(i;i<=b;i++) ^ user.c:7:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("difprim.in","r",stdin); ^ user.c:8:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("difprim.out","w",stdout); ^ user.c:10:10: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&a,&b); ^