#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
int n,v[801];

ifstream f("nrtri.in");
ofstream g("nrtri.out");

int cautbin(int i,int j)
{
    int suma=v[i]+v[j];
    int p=j+1,u=n,poz=-1;
    while(p<=u)
    {
        int m=(p+u)/2;
        if(v[m]<suma)
        {
            p=m+1;
            poz=m;
        }
        else u=m-1;
    }
    return poz;
}

int main()
{
    int suma=0;
    f>>n;
    for(int i=1;i<=n;i++)f>>v[i];
    sort(v+1,v+n+1);
    for(int i=1; i<n-1; i++)
        for(int j=i+1; j<n; j++)
            if(cautbin(i,j)!=-1)suma+=cautbin(i,j)-j;
    g<<suma;
    return 0;
}