#include <fstream>
#include <algorithm>

using namespace std;
    ifstream f("nrtri.in");
    ofstream g("nrtri.out");

int main()
{  int n, a[8002], nr=0;
    f>>n;
    for (int i=1; i<=n; ++i)
        f>>a[i];
    sort(a+1, a+n+1);
    for (int i=1; i<=n-2; ++i)
        for (int j=i+1; j<=n-1; ++j)
            for (int k=j+1; k<=n; ++k)
                if (a[i]+a[j]>=a[k]) nr++;
                    else break;
    g<<nr;
    return 0;
}