#include<cstdio>
#include<algorithm>
using namespace std;
int v[3001];
int main()
{
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	int n,ok,m,m1,x,y,i,j,a,b,nr=0,ok1;
	scanf("%d",&n);
	for(i=1;i<=n;i++)scanf("%d",&v[i]);
	sort(v+1,v+n+1);
	for(i=1;i<=n-2;i++)
		for(j=i+1;j<=n-1;j++)
		{
			a=v[i]+v[j];
			b=v[j]-v[i];
			ok=1;ok1=1;
			for(m=j+1;m<=n&&ok;m++)
				if(v[m]>=b)ok=0;
			for(m1=m-1;m1<=n&&ok1;m1++)
				if(v[m1]<=a)ok1=0;
			if(!ok1)nr+=m1-m+1;
		}
	printf("%d",nr);
	return 0;
}