#include <fstream>
#include <algorithm>
#define MAXIM 1001
using namespace std;
ifstream in("nrtri.in");
ofstream out("nrtri.out");
int N,sol,V[MAXIM];
void read_data()
{
    in>>N;
    for(int i=1;i<=N;i++)
        in>>V[i];
}

void solve()
{
    sort(V+1,V+N+1);
    for(int i=1;i<=N;i++)
    {
        for(int j=i+1;j<=N;j++)
        {
            int m,st,dr;
            st=j+1;dr=N;
            while(st<=dr)
            {
                m=(st+dr)/2;
                if(V[m]<=V[i]+V[j]) st=m+1; else dr=m-1;
            }
            sol+=dr-j;
        }
    }
    out<<sol;
}

int main()
{
    read_data();
    solve();
    return 0;
}