#include<stdio.h>
int main()
{
	int i,n,a,x,v[30000],t=0,gata;
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	scanf("%d",&n);
	for(i=0;i<n;i++)
	scanf("%d",&v[i]);
	do{
		gata=1;
		for(i=0;i<n-1;i++)
		if(v[i]>v[i+1])
		{
			t=v[i];
			v[i]=v[i+1];
			v[i+1]=t;
			gata=0;
		}
	}while(!gata);
		t=0;
	for(i=0;i<n-2;i++)
		for(a=i+1;a<n-1;a++)
			for(x=a+1;x<n;x++)
				if(v[i]+v[a]>=v[x])
					t++;
				else
					break;
	printf("%d",t);
	return 0;
}