#include<fstream>
#include<algorithm>
using namespace std;
int a[801],n,i,j,k,h,s;
int main ()
{
    ifstream f("nrtri.in");
    ofstream g("nrtri.out");
    f>>n;
    for(i=1;i<=n;i++) {f>>a[i];}
    sort(a,a+n+1);
    for(i=1;i<n-1;i++)
    for(j=i+1;j<n;j++)
   {s=a[i]+a[j];
    for(h=j+1;h<=n;h++)
        if(s>=a[h]) k++;
        else h=n+1;}
    g<<k<<" ";
    return 0;
}