Compilare: user.c: In function ‘main’: user.c:20:64: warning: operation on ‘u’ may be undefined [-Wsequence-point] for(c[++u]=d[i];u>2&&S(c[u-2],c[u],c[u-1])>0;c[u-1]=c[u--]); ^ user.c:22:68: warning: operation on ‘v’ may be undefined [-Wsequence-point] for(e[++v]=d[i];v>2&&S(e[v-2],e[v],e[v-1])<0;e[v-1]=e[v--]); ^ user.c:13:9: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("infasuratoare.in","r",stdin),freopen("infasuratoare.out","w",stdout),scanf("%d",&n); ^ user.c:13:47: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("infasuratoare.in","r",stdin),freopen("infasuratoare.out","w",stdout),scanf("%d",&n); ^ user.c:13:85: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] freopen("infasuratoare.in","r",stdin),freopen("infasuratoare.out","w",stdout),scanf("%d",&n); ^ user.c:15:11: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lf%lf",&d[i].x,&d[i].y); ^