#include <iostream>
#include <fstream>
using namespace std;
int n,a[805],nrtri,i,j,k;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");
int main()
{
    fin>>n;
    for(i=1;i<=n;i++)fin>>a[i];
    for(i=1;i<=n;i++)
    {
        for(j=i+1;j<=n;j++)
        {
            for(k=j+1;k<=n;++k)
            {
                if(a[i]<=a[j]+a[k] && a[j]<=a[k]+a[i] && a[k]<=a[i]+a[j])nrtri++;
            }
        }
    }
    fout<<nrtri;

}