#include <iostream>
#include <fstream>

using namespace std;

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

int i,j,n,k,t,p,nr=0;
int* v;

void quick(int s,int d)
{
    int i,j,x,t;
    i=s;
    j=d;
    x=v[(i+j)/2];
    do
    {
        while(v[i]<x)
            i++;
        while(v[j]>x)
            j--;
        if(i<=j)
        {
            t=v[i];
            v[i]=v[j];
            v[j]=t;
            i++;
            j--;
        }
    }while(i<=j);
    if(i<d)
        quick(i,d);
    if(j>s)
        quick(s,j);
}
int main()
{
    f>>n;
    v=new int[n+4];
    for(i=1;i<=n;i++)
        f>>v[i];
    quick(1,n);
    k=1;
    for(i=1;i<=n-1;i++)
    for(j=i+1;j<=n-2;j++)
    {
        k=j+1;
        if(v[i]+v[j]>=v[k] && k<=n)
            ++k;
        nr=nr+k-j-1;
    }
    g<<nr;
}