#include <fstream>
#include <algorithm>
using namespace std;
int n,v[801],i,j,p,q,m,p1,q1,dif,nrt;
long s;
int main()
{
    ifstream fin ("nrtri.in");
    ofstream fout ("nrtri.out");
    fin>>n;
    for (i=1;i<=n;i++)
        fin>>v[i];
    sort (v+1,v+n+1);
    for (i=1;i<n;i++)
    for (j=i+1;j<=n;j++)
    {
        s=v[i]+v[j];
        dif=v[j]-v[i];
        p=j+1;
        q=n;
        while (p<=q)
        {
            m=(p+q)/2;
            if (v[m]>=s) {p=m+1;}
            else q=m-1;
        }

        p1=j+1;
        q1=n;
        while (p1<=q1)
        {
            m=(p1+q1)/2;
            if (v[m]<dif) {p1=m+1;}
            else q1=m-1;
        }
        nrt=nrt+(q-(p1-1));
    }
    fout<<nrt;
    return 0;
}