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

using namespace std;

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

const int NMAX = 800;
int v[NMAX+1];


int CB(int low,int high,int x)
{
    int pw2=1;
    while(pw2<high-low+1)
    {
        pw2=pw2*2;
    }
    pw2=pw2/2;
    int sol = low;
    for(; pw2>=1; pw2=pw2/2)
    {
        if(sol+pw2<=high && v[sol+pw2]<=x)
            sol+=pw2;
    }

    if(sol==low && v[sol]>x)
        return -1;
    else
        return sol;
}

int Solve(int n)
{
    int sol=0;
    for(int i=1; i<=n-2; i++)
    {
        for(int j=i+1;j<=n-1;j++)
        {
            int k=CB(j+1,n,v[i]+v[j]);
            if(k!=-1)
                sol+=k-j;
        }
    }
    return sol;
}

int main()
{
    int n;
    in>>n;
    for(int i=1; i<=n; i++)
    {
        in>>v[i];
    }
    sort(v,v+n);
    out<<Solve(n);

}