#include<fstream>
using namespace std;
int n,i,j,aux,nr,k,a[801];
int main()
{
ifstream f("nrtri.in");
ofstream g("nrtri.out");
f>>n;
for(i=1;i<=n;i++)
f>>a[i];
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;i++)
for(j=i+1;j<=n;j++)
for(k=j+1;k<=n;k++)
if(a[i]+a[j]>=a[k])
nr++;
g<<nr;
return 0;
}