#include <fstream>

using namespace std;

long int i,j,aux,nr,a[805],k,n,p;

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;
        }
        nr=0;
    for (i=1;i<=n-2;i++)
        for (j=i+1;j<=n-1;j++)
        for (k=j+1;k<=n;k++)
            if (a[k]<=a[i]+a[j])
            nr=nr+1;
            g<<nr;
            f.close();
            g.close();
    return 0;
}