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

using namespace std;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");
int v[803];
int main()
{int n;
fin>>n;
for (int i=1;i<=n;i++)
    fin>>v[i];
sort (v+1,v+n+1);
int nr=0;
for (int i=1;i<=n-2;i++)
    for (int j=i+1;j<=n-1;j++){
    ///caut binar cea mai din dreapta valoare cu proprietatea ca <= decat v[i]+v[j]
    int st=j+1, dr=n, p=0;
    while (st<=dr){
        int mid=(st+dr)/2;
        if (v[mid]<=v[i]+v[j]){
            p=mid;
            st=mid+1;
        }
        else
            dr=mid-1;
    }
    if (p!=0)
        nr=nr+p-j;
}
  fout<<nr;
}