#include <fstream>
#include <algorithm>

using namespace std;
ifstream cin ("nrtri.in");
ofstream cout ("nrtri.out");
int v[801];
int main()
{
    int n,c=0,i,i2,i3;
    cin>>n;
    for (i=0;i<n;i++)
        cin>>v[i];
    sort(v,v+n);
    for (i=0;i<n-2;i++)
    {
        for(i2=i+1;i2<n-1;i2++)
        {
            for(i3=i2+1;i3<n;i3++)
            {
                if (v[i]+v[i2]<v[i3])
                    break;
                else c++;
            }
        }
    }
    cout<<c;
    return 0;
}