#include <fstream>
#include <algorithm>
using namespace std;
ifstream fi("nrtri.in");
ofstream fo("nrtri.out");

int i,j,k,X[801],n,cnt;
int main()
{
    fi>>n;
    for (i=1; i<=n; i++)
        fi>>X[i];
    sort(X+1,X+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 (X[k]<=X[i]+X[j])
                    cnt++;
                else
                    break;
            }
    fo<<cnt;
    fi.close();
    fo.close();
    return 0;
}