Compilare: user.c: In function ‘main’: user.c:12:5: warning: use of ‘ll’ length modifier with ‘f’ type character [-Wformat=] printf("%llf",fabs(s/2.0)); ^ user.c:7:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("aria.in","r",stdin),freopen("aria.out","w",stdout),scanf("%d",&n); ^ user.c:7:41: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("aria.in","r",stdin),freopen("aria.out","w",stdout),scanf("%d",&n); ^ user.c:7:70: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] freopen("aria.in","r",stdin),freopen("aria.out","w",stdout),scanf("%d",&n); ^ user.c:9:14: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lf%lf",&v[i].x,&v[i].y); ^