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