#include <fstream>
#include <algorithm>
using namespace std;
ifstream in ("nrtri.in");
ofstream out ("nrtri.out");
int n,v[2001],rez;
int main()
{
    in>>n;
    for(int i=1;i<=n;i++)
        in>>v[i];
    int a,st,dr,mid;
    sort(v+1,v+n+1);
    for(int i=1;i<=n-1;i++)
        for(int j=i+1;j<=n;j++)
        {
            st=1;
            dr=n;
            while(st<=dr)
            {
                mid=(st+dr)/2;
                if(v[mid]<=v[i]+v[j] && mid!=i && mid!=j)
                {
                    rez++;
                    st=mid+1;
                }
                else
                    dr=mid-1;

            }
        }
    out<<rez/3;
    return 0;
}