#include <fstream>//varianta II  ?p
using namespace std;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
int i,j,k,n,t,a[1000];
int main()
{
    f>>n;
    for(i=1;i<=n;i++)f>>a[i];
    for(i=1;i<=n-2;i++)
      for(j=i+1;j<=n-1;j++)
        for(k=j+1;k<=n;k++)
         if(a[i]+a[j]>=a[k]&&a[i]+a[k]>=a[j]&&a[k]+a[j]>=a[i])t++;
    g<<t<<'\n';
    g.close();
    return 0;
}