#include <fstream>
#include <algorithm>

using namespace std;

int v[810];
int n, i, sol, j, k;

int main () {
    ifstream fin ("nrtri.in");
    ofstream fout("nrtri.out");

    fin>>n;
    for (i=1;i<=n;i++)
        fin>>v[i];

    sort(v+1, v+n+1);

    for (i=1;i<=n-2;i++)
        for (j=i+1;j<=n-1;j++)
            for (k=j+1;k<=n;k++)
                if (v[i] + v[j] >= v[k])
                    sol++;
    fout<<sol;
    return 0;
}