#include<bits/stdc++.h>
#define mp make_pair
#define PII pair<int,int>
#define fi first
#define se second
using namespace std;

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

const int NMAX=805;

int n,a[NMAX];
int sol;

int main()
{
    int i,j,top;
    fin>>n;
    for (i=1;i<=n;i++) fin>>a[i];
    sort(a+1,a+n+1);
    for (i=3;i<=n;i++)//cea mai mare latura
    {
        top=0;
        for (j=2;j<i;j++)
        {
            while ((top+1)<j && a[top+1]<(a[i]-a[j])) top++;
            sol+=top;
        }
    }

    fout<<sol<<"\n";
    return 0;
}