Compilare: user.c: In function ‘main’: user.c:9:27: warning: variable ‘x’ set but not used [-Wunused-but-set-variable] unsigned long a,b,i,j,x,y; ^ 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("%lu",&a); ^ user.c:11:10: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lu",&b); ^