#include <fstream>
#include <algorithm>
using namespace std;
short int a[801],y,z,m,n,h,l,i,j;
int nrtri=0;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
bool cmp(int a,int b)
{
    return a<b;
}
void citiresortare()
{
    f>>n;
    for (i=1;i<=n;i++) f>>a[i];
    sort (a+1,a+n+1,cmp);
}
void fixareaflarenumar()
{
    for (i=1;i<=n-2;i++)
       for (j=i+1;j<=n-1;j++)
       for (z=j+1;z<=n;z++)
       if (a[i]+a[j]>=a[z]) nrtri++;
       else break;

}
int main()
{
    citiresortare();
    fixareaflarenumar();
    g<<nrtri;
    return 0;
}