#define f(P,Q,R)for(l=1,r=n;l<r;P)a[l]Q-a[r]?s++,R:0;s=!printf("%d ",s);
a[1<<18],n,x,s;
c(int*a,int*b){x=*a-*b;}
main(l,r){
	for(;~scanf("%d",a+n++););
	qsort(a+1,n-=2,4,c);
	f(r--,<,l++)f(l++,>,r--)f(a[l]+a[r]<=0?r-=a[l++]==-a[r]:r--,==,0);
}