#include <fstream>
#include <algorithm>

#define DIM 803
using namespace std;
ifstream fin("transport.in");
ofstream fout("transport.out");

int v[DIM];

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 proprietatate 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;
    return 0;
}