#include<iostream.h>
#include<fstream.h>
ifstream f("nrtri.in");
ofstream g("nrtri.out");

int main()
{
    int n,i,j,k,a[1001],q=0,aux;
    f >> n;
    for(i=1;i<=n;i++)
        f >> a[i];
	f.close();
	for (i=1; i<=n-1; i++)
		for (j=i+1; j<=n; j++)
		if (a[i]>a[j])
		{
			aux=a[i];
			a[i]=a[j];
			a[j]=aux;
		}
    for(i=1;i<=n-2;i++)
        for(j=i+1;j<=n-1;j++)
			for (k=j+1; k<=n && a[i]+a[j]>=a[k]; k++)
					q++;
    g << q;
	g.close();
    return 0;
}