#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");
#define MAX 810
int main()
{
    int n,a[MAX],k=0,j,z;
    fin >> n;
    int i;
    for(i=1;i<=n;i++)
        fin >> a[i];
    sort(a+1,a+n+1);
    for(i=1;i<=n-2;i++)
        for(j=i+1;j<=n-1;j++)
            for(z=j+1;z<=n;z++)
            {if(a[i]+a[j]>=a[z])
                        k++;
            else
                    break;
            }
    fout << k<< "\n";
    return 0;
}