#include <fstream>
#include <algorithm>

using namespace std;

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

int main()
{
    int n, v[1001], i, moduri=0, j, aux, k;
    in>>n;
    for(i=1; i<=n; i++)
        in>>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 && v[k]<=v[i]+v[j]; k++)
        moduri++;
    out<<moduri;
    return 0;
}