Compilare: user.c: In function ‘main’: user.c:4:9: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("dmin2.in","r",stdin),freopen("dmin2.out","w",stdout),scanf("%lld%lld",&n,&m),printf("%lld",(n-2)*(n-1)/2-m); ^ user.c:4:39: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("dmin2.in","r",stdin),freopen("dmin2.out","w",stdout),scanf("%lld%lld",&n,&m),printf("%lld",(n-2)*(n-1)/2-m); ^ user.c:4:69: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] freopen("dmin2.in","r",stdin),freopen("dmin2.out","w",stdout),scanf("%lld%lld",&n,&m),printf("%lld",(n-2)*(n-1)/2-m); ^