Compilare: main.c: In function 'main': main.c:8:28: warning: unused variable 'r' [-Wunused-variable] unsigned long long a,b,r; ^ main.c:6:5: warning: ignoring return value of 'freopen', declared with attribute warn_unused_result [-Wunused-result] freopen("cmmdc.in","r",stdin); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~ main.c:7:5: warning: ignoring return value of 'freopen', declared with attribute warn_unused_result [-Wunused-result] freopen("cmmdc.out","w",stdout); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ main.c:9:5: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result] scanf("%llu%llu",&a,&b); ^~~~~~~~~~~~~~~~~~~~~~~