#include <fstream>
#include <algorithm>

using namespace std;

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

int n;
int a[1000];


int main()
{
    int k,nr,i,j;
    f>>n;
    for(i=1;i<=n;i++)
        f>>a[i];
    sort(a+1,a+n+1);
    nr=0;
    for(i=1;i<=n-2;i++)
        for(j=i+1;j<=n-1;j++)
    {
        k=j+1;
        while(a[i]+a[j]>=a[k] && k<=n)
              k++;
        nr=nr+k-j-1;
    }
    g << nr;
    return 0;
}