#include <fstream>
#include <algorithm>
using namespace std;
int main()
{
    ifstream  f("nrtri.in");
    ofstream g("nrtri.out");
    int v[802],i,n,j,k,cont=0;
    f>>n;
    for (i=1; i<=n; i++)
    f>>v[i];
    sort(v+1,v+n+1);
    for (i=1; i<=n-2; i++)
    for (j=i+1; j<=n-1; j++)
    for (k=j+1; k<=n; k++)
    if (v[i]+v[j]>=v[k])
    cont++;
    else
    break;
    g<<cont;
    return 0;

}