#include <iostream>
#include <fstream>
#include <algorithm>

using namespace std;

ifstream fin("nrtri.in");
ofstream fout("nrtri.out");

int n, v[801], nr;
int L=9;  //2^9 = 512 < 800

bool cmp (int x, int y)
{
    return (x < y);
}

int cautare(int a, int b)
{
    int pas=1<<L;
    int i=0;
    while(pas!=0)
    {
        if(i+pas <= n && v[i+pas] <= v[a]+v[b])
            i+=pas;
        pas/=2;
    }
    return i;
}

int main()
{
    int i,j,k;
    fin>>n;
    for(i=1; i<=n; i++)
        fin>>v[i];

    sort(v+1,v+n+1,cmp);

    for(i=1; i+1<n; i++)
        for(j=i+1; j<n; j++)
        {
            k=cautare(i,j);
            if(k>j)
            {
                nr+=k-j;
                //cout<<v[i] << " " << v[j] << " " << v[k]<<"\n";
            }
        }
    fout<<nr;
}