#include <fstream>
#include <algorithm>
using namespace std;
ifstream in("nrtri.in");
ofstream out("nrtri.out");
int v[801];
int main()
{
    int n, i, j, k, cnt=0, s2, l3;
    in>>n;
    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++)
            for (k=j+1; k<=n; k++)
            {
                    s2=v[i]+v[j];
                    l3=v[k];
                    if (s2>=l3)
                        cnt++;
                    else
                        break;
            }
    out<<cnt;
    return 0;
}