#include <fstream>
#include <algorithm>
#include <vector>

using namespace std;

int v[10000], rasp=0;

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

int main()
{
    int n, k, sol=0;
    in>>n;
    for(int i=1; i<=n; i++){
        in>>v[i];
    }
    sort (v+1, v+n+1);
    for(int i=1;i<=n-2;i++){
        for(int j=i+1;j<=n-1;j++){
            for(int r=j+1;r<=n;r++){
                if(v[i]+v[j]>=v[r])
                        sol++;
                else
                   break;

            }
        }

    }
    out<<sol;
    in.close();
    out.close();
    return 0;
}