Compilare: user.c: In function ‘main’: user.c:5:10: warning: unused variable ‘r’ [-Wunused-variable] int a,b,r; ^ user.c:6:9: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("cmmdc.in","r",stdin); ^ user.c:7:9: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("cmmdc.out","w",stdout); ^ user.c:8:7: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&a,&b); ^