#include <fstream>

using namespace std;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
int main()
{
    int n,a[801],i,j,k,nr=0,aux;
    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-2;i++)
        for(j=i+1;j<=n-1;j++)
        for(k=j+1;k<=n;k++)
        if(a[i]+a[j]>=a[k])nr++;
        else break;
    g<<nr;
    return 0;
}