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

using namespace std;

const int maxn=801;

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

int N,v[maxn];
void Read()
{
    f>>N;
    for (int i=0; i<N; i++)
        f>>v[i];
    sort(v,v+N);
}
int Binary_Search(int left,int right,int LgMin)
{
    int poz=0,PrimaLatura=left;
    while(left<=right)
    {
        int mid = (left + right) / 2;
        if (v[mid]<=LgMin)
        {
            poz=mid;
            left=mid+1;
        }
        else right=mid-1;
    }
    if (poz==0) return 0;

    return poz-PrimaLatura+1;
}
void Solve()
{
    int Ans=0,i,j;
    for (i=0; i<N-1; i++)
        for (j=i+1; j<N-1; j++)
            Ans+=Binary_Search(j+1,N-1,v[i]+v[j]);
    g<<Ans;
}
int main()
{
    Read();
    Solve();
}