#include <iostream>
#include <fstream>

using namespace std;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
int bule(int (&v)[1000], int n)
{
    int ok,i,aux;
    do
    {
        ok=1;
        for(i=1; i<=n-1; i++)
            if(v[i]>v[i+1])
            {
                ok=0;
                aux=v[i];
                v[i]=v[i+1];
                v[i+1]=aux;
            }
    }
    while(ok!=1);
}
int main()
{
    int N,v[1000],i,t=0,k,j,x;
    f>>N;
    for (i=1; i<=N; i++)
        f>>v[i];
    bule (v,N);
    for (i=1; i<=N; i++)
        for (j=i+1; j<=N; j++)
        {
            x=v[i]+v[j];
            k=j+1;
            while (x>=v[k]&&k<=N)
            {
                t++;
                k++;
            }
        }
    g << t << endl;
    return 0;
}