Compilare: user.c: In function ‘main’: user.c:10:5: warning: implicit declaration of function ‘fabs’ [-Wimplicit-function-declaration] printf("%.5lf",fabs(s)); ^ user.c:10:20: warning: incompatible implicit declaration of built-in function ‘fabs’ [enabled by default] printf("%.5lf",fabs(s)); ^ user.c:5:12: 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",&n); ^ user.c:5:41: 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",&n); ^ user.c:5:70: 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",&n); ^ user.c:7:14: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lf%lf\n",x+i,y+i); ^