#include <fstream>
#include <algorithm>
/*#INCLUDE <VALOARE>
#INCLUDE <BO$$>
#INCLUDE <NOT_BUREA>
#INCLUDE <BIBLIA>*/
using namespace std;
ifstream in("nrtri.in");
ofstream out("nrtri.out");
int n,v[801],nr,i,j;
int main()
{
    in>>n;
    nr=0;
    for(i=1; i<=n; i++)
        in>>v[i];
    sort(v+1,v+n+1);
    for(i=1; i<=n-2; i++)
        for(j=i+1; j<=n-1; j++)
        {
            int k=j+1;
            while(v[i]+v[j]>=v[k] && k<=n)
                k++;
            nr+=k-j-1;
        }
    out<<nr;
    return 0;
}