#include <fstream>
#include <algorithm>

using namespace std;

ifstream cin("nrtri.in");
ofstream cout("nrtri.out");

int v[801];

int main()
{
    int n, s, st, dr, mij, sol, i, j;
    long long int cnt=0;
    cin>>n;
    for(i=1;i<=n;i++)
    {
        cin>>v[i];
    }
    sort(v+1,v+n+1);

    for(i=1;i<=n;i++)
    {
        for(j=i+1;j<=n;j++)
        {
            s=v[i]+v[j];
            st=j+1;
            dr=n;
            sol=j;
            while(st<=dr)
            {
                mij=(st+dr)/2;
                if(v[mij]<=s)
                {
                    sol=mij;
                    st=mij+1;
                }
                else
                    dr=mij-1;
            }
            cnt+=sol-j;

        }
    }
    cout<<cnt;
    return 0;
}