Compilare: user.c: In function ‘main’: user.c:7:5: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("cmmdc.in","r",stdin); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~ user.c:8:5: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("cmmdc.out","w",stdout); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ user.c:9:5: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&a,&b); ^~~~~~~~~~~~~~~~~~~